The Reaping Mauler would be so disappointed. This is what his art became. Holding someone still for a few rounds. 

Watch a single Bow and arrow choke and then tell me this is grappling competence. 

Definitely need to get some chokes and joint locks. Heel hook and their movement is toast. Submission taps also.

How do you get a "feat buff".  I'm a really bad DM, pretty new...

Don't ever put yourself down dude. Unless you truly F it up royal. As for how do players get feats, they can optionally chose a feat instead of the ability score increase they usually get every 4 levels or so. Fighters and Rouges get more than usual as they level and Variant Humans can start with one.

 I'm confused..so both creature become restrained, meaning. You get advantage for attacking a restrained and the feats feature creature yet you lose that advantage for being restrained since any amount of advantage cancels disadvantage or the other way around.

So you literally get nothing for pinning the enemy. If anything you make yourself more vulnerable. 

What is "interesting" about this feat, is that it doesn't actually make you better at grappling, or at maintaining a grapple. At all.

At the very least I would have expected a feat called "Grappler" to give you advantage on Strength (Athletics) checks for grappling.

Both become restrained but they are still grappled. You should still have advantage on attacks for being in a grapple.

The tradeoff is you are giving advantage to your allies to attack the foe in exchange for you also taking those disadvantages from other foes

Restrained
A restrained creature's speed becomes 0, and it can't benefit from any bonus to its speed.
Attack rolls against the creature have advantage, and the creature's attack rolls have disadvantage. **
The creature has disadvantage on Dexterity saving throws.

** (these cancel each other out between the two in the grapple so it would stay a straight roll, but it shouldn't cancel grapple advantage )

PS Grapple is an attack so you should have advantage to go for the pin

Grappling

When you want to grab a creature or wrestle with it, you can use the Attack action to make a special melee attack, a grapple. If you're able to make multiple attacks with the Attack action, this attack replaces one of them.

The target of your grapple must be no more than one size larger than you and must be within your reach. Using at least one free hand, you try to seize the target by making a grapple check instead of an attack roll: a Strength (Athletics) check contested by the target's Strength (Athletics) or Dexterity (Acrobatics) check (the target chooses the ability to use). You succeed automatically if the target is incapacitated. If you succeed, you subject the target to the grappled condition. The condition specifies the things that end it, and you can release the target whenever you like (no action required).

Escaping a Grapple. A grappled creature can use its action to escape. To do so, it must succeed on a Strength (Athletics) or Dexterity (Acrobatics) check contested by your Strength (Athletics) check.

Moving a Grappled Creature. When you move, you can drag or carry the grappled creature with you, but your speed is halved, unless the creature is two or more sizes smaller than you.

This is kind of a niche feat, but it's usable! Here's an example:

I am running a rogue/fighter with expertise in athletics. This character has a +11 to succeed on grapple checks. As long as he has an enemy grappled with this feat, he is almost guaranteed to murder them soon after, making two attacks at advantage and proc'ing sneak attack every turn. Add in the fact that if you shove your enemy prone, they need LifeAlert because they've fallen and can't get up because they have no movement to stand, and now a friend can join you in attacking at advantage in melee range. The fun part is he uses a whip, so a lot of these attacks I get to describe as him viciously garroting baddies. 

As for the last part, I can see that being useful if you are attempting to capture someone, or if you are down to the last enemy in an encounter, and would like to just sit on him for your friends to finish off. Alternatively, you can single out an enemy for the wizard to destroy when they fail their Dex save because they cant dodge lol. If there's another rogue in the party, you just became his best friend. The pinning ability plays well with others.

This gets a lot of hate, but seems much better than shield master and even on a par with tavern brawler.  What am I missing?

Shield Master:

Once you knock the mob PRONE, you have to drop your weapon to GRAPPLE them.   Doffing and donning a shield takes a whole action.

So your further attacks are unarmed.  No divine smites, no weapon bonuses.

If you want to use weapon again you have to use an entire round to get rid of your shield and pick up weapon.

Tavern Brawler:

Using an improvised weapon in main hand, let's call it "shield", so still get +2 to AC.

1st attack: Hit with the shield for some damage.

2nd attack: SHOVE PRONE with free hand.

Bonus Action: GRAPPLE with free hand.

Rest of attacks are hit twice with shield WITH ADVANTAGE. And the mob has DISADVANTAGE to hit me.  Downside: Ranged attacks hit the mob with DISADVANTAGE.

GRAPPLER:

Proper Weapon in main hand.  NO SHIELD in other. (-2 AC).

1st attack: GRAPPLE with free offhand.

2nd attack: hit with main weapon with ADVANTAGE.

Bonus Action: Free for Spiritual Weapon, Dash or whatever you've got.

Rest of attacks are hit twice with proper weapon WITH ADVANTAGE, and use the mob as a meat shield for half cover, so get +2 AC again.  As mob isn't prone, rest of the team can attack the normally.  Only dowsnide is that the mob can attack me normally.  But at least thats crowd control of sorts, and my Armor of Agathys will help.

 EDIT: Obviously not using the optional part of GRAPPLER: "You can use your action to try to pin a creature grappled by you. To do so, make another grapple check. If you succeed, you and the creature are both restrained until the grapple ends."

how is this in the basic rules, it is not so why does it say so

The trouble is the advantage element can be gained just by shoving them prone with a second attack.

So on your turn: Grapple>Shove. Enemy is prone and can't get up. If you happen to have a third attack you can swing at them at advantage (Sans two handers obviously but the advantage does cancel out the two handed disadvantage).

Ranged attacks will have disadvantage, yes, but you can then drag the enemy around if need be. And the person attacking from afar can either use a saving throw spell for damage, or if they're a ranger/rogue with a bow pick a different target or get in and join in the roflstomping.

It just isn't worth the feat for advantage on a grappled creature and only for yourself (If you're doing grapples, you're not going for DPR, you're helping your team get hits in), in fact none of the above feats save maybe shield master really help with grappling>shoving itself tbh. And yeah the added part about restraining yourselves is just worthless since restraining yourself is dumb as heck. You basically remove yourself from the fight while making it easier for enemies to hit you. Why would you ever want that? Ever? If it just restrained the enemy then sure, great. But restraining yourself as well? Really? Just grapple and shove prone, basically the same thing and you don't hamstring your character as well in the process.

Additionally, while prone the enemy has disadvantage on ALL attacks made. But they can't get up while you still have them grappled. So while ranged atatcks on them have disadvantage, the upside is all melee attacks on them have advantage and all attacks -they- make are at disadvantage. I say the pros far outweigh the cost, and best of all it didn't use up a precious ASI to achieve it!

Many people miss the point of this feat.  In a 1v1, YOU gain the advantage on the attack role.  If you succeed on restraining the target, your PARTY gains advantage. Huge if you aren't using flanking rules

@Solgard True, but you're also putting yourself into harms way if you're fighting more than this grappled monster since all attacks against you now have advantage. It seems good in a single target fight, or maybe a fight with multiple enemies if most of them aren't a threat to the grappler. Otherwise, it definitely seems risky. Edit: although if you're playing a Barb and using Reckless often then there's not much change regarding your defense I guess.

@mamergamer "Both become restrained but they are still grappled. You should still have advantage on attacks for being in a grapple." You do still have advantage on attacks against the grappled targer, which offsets the disadvantage you have on attacks for being restrained. So any attacks or additional grapple attempts would be a straight roll for the grappler.

Edit: @RanorBrightmane "And yeah the added part about restraining yourselves is just worthless since restraining yourself is dumb as heck. You basically remove yourself from the fight while making it easier for enemies to hit you. Why would you ever want that? Ever? If it just restrained the enemy then sure, great. But restraining yourself as well? Really? Just grapple and shove prone, basically the same thing and you don't hamstring your character as well in the process."

I gotta assume you're not coming at this from the perspective of a Barb because they make it easier for enemies to hit themselves all the time. As noted above in a previous edit, you would incur no additional penalty regarding defense if you are using Reckless Attacks. The only additional penalty is to movement, but you can break the grapple as a free action if you truly need to move. You're also not considering the effect pinning the target would have on the rest of the group. Pinning provides the same benefits to melee attacks as knocking prone, but pinning also gives advantage to ranged attacks AND gives disadvantage on DEX saves. The more I think about this feat, the better it's seeming to me (if only really on a Barb with decent defense options and heals available).

TLDR: If you have a large group and are free to attack recklessly on the regular, then this feat seems pretty good actually. It's 2x (please correct my math if it's wrong) better than knocking the target prone for your ranged party members and gives the target disadvantage on DEX saves. The only cost for a reckless barbarian is giving up advantage on attacks against the target. Seeing as the main benefit is giving advantage to your entire party, this value obviously scales on how often your teammates are attacking with advantage (my group isn't using flanking rules so I'm very much considering grabbing this at 8 or 12 if my team is struggling to hit). 

Couldn't agree more man.

A lizardfolk could grapple someone and than keep biting him for 1d6+strength really good for the martial classes like barbarian and fighter

This seems like such a weak feat. 
It should come with +1 STR or DEX, for sure, I'm not sure how you gain significant training as a grappling fighter without improving anything; a tavern brawler gets to improve STR or CON, for comparison. 

Also you have advantage against a creature you're already grappling - no advantage to actually grab them? 

And you can "pin" for "both restrained" which is basically useless, not any of the other cool things we see grapplers do in the UFC? 

If you've actually taken this Feat and think it's worth it I'd love to hear from you :)

I just don't get this feat... there are better options why waste yourself on this feat? 

you get advantage on attack rolls against a creature you are grappling... is the only good feature... its hardly a great for a cost of a feat. Grappling is limited to begin with! they must be less than one size category of you aka small, medium or large unless you turn into a bear or enlarge person. its better to take tavern brawler... push-> bonus action grapple attack when the person is down. Then you have d4 unarmed strike and have +1 to str or con

Quote from taven03 >>

I just don't get this feat... there are better options why waste yourself on this feat? 

you get advantage on attack rolls against a creature you are grappling... is the only good feature... its hardly a great for a cost of a feat. Grappling is limited to begin with! they must be less than one size category of you aka small, medium or large unless you turn into a bear or enlarge person. its better to take tavern brawler... push-> bonus action grapple attack when the person is down. Then you have d4 unarmed strike and have +1 to str or con

Pinning is actually quite nice because of the disadvantages it imposes. Attack advantages are always nice and many of the strongest spells like disintegrate rely on Dex saves.

Something changed on this feat? I used to see in places that it took away the automatic success for a creature one size larger to escape your grapple, which I figured was probably the best part of the feat (that with the advantage made me consider it for a grappler I built).

Now it's definitely not worth it for me.

That's what I was thinking, this is useless in a fight with multiple enemies attacking you.