It can move its entire movement range each turn. You as a player can also move 10 ft attack move abother 10 ft attack again and use remaining 10ft movement

try giving this dragon's breath

Okay, but what if my owl familiar delivers a shocking grasp spell for me (on my turn, using my action and its reaction), depriving the target of its reaction, then uses the help action on its own turn, helping another party member to hit?

This, of course, presumes that I go before the owl.

Quote from RevokFarthis >>

All familiars are powerful, but the Owl familiar makes an excellent scout, and with it's bonuses to perception, ability to escape opportunity attacks, ability to move stealthily in the air, it can be an unstoppable engine of death and destruction for any properly shenanigan inclined wizard, even at high levels:

(utility)
"Wizard, why didn't you rest? We're preparing to assault the castle!"
"Hmm? Oh, while you rested I prepared Glyphs of Warding at key locations along the enemies defenses."

(direct combat)
"A bolt of brown and white, a flurry of feathers, streaks down from the sky and briefly alights on the Dark Knight's steel helm. Suddenly arcs of energy dance across his shiny plate mail dealing (cantrip dice) lightning damage! Before he or his minions can react; Angmar, Destroyer of action economies takes back to the air, safely out of reach."

(encounter cheesing)
"The Minotaur lifts his greataxe, preparing to sink it deep into the Rogue's neck, when suddenly; with a shudder and a failed Charisma save, it winks out of existance, and a Familiar (thrice-cursed by the DM) Owl is in it's place. The Minotaur finds itself drifting helplessly through the astral plane."

Pair it with a Ring of Spell Storing, if your DM is lenient/mad/asleep enough to let you find one, for more sillyness:

(AoE mob clearing, or taking care of entire encounters on your own while you and your party safely sip tea from 100ft away)
"It is a dark, moonless night, all is silent in the bandit camp when out of the sky comes crashing down a 5th level Fireball to burn the camp and all inside to ash."

(Make an example of someone)
"the thief was running, but he wasn't moving, what was going on? An uneasy sensation, the ground was pulling away from him, he was... flying? No, floating! He couldn't control it! He turned to look around for a source when he saw; the man he'd pickpocketed, a wizard?
The Wizard stared at him, he muttered quiet words and his eyes glowed a reddish orange, and on his shoulder sat... an owl? Are it's eyes glowing yellow?
In an instant these thoughts meant little more to the thief as a cloud of sharp spinning blades errupted into existance around him, churning his flesh to bloody ribbons and viscera scattered and splattered across the town square."

 Dude, you're pretty harsh on pickpockets 

Snicker..  My Noble Knight.
(minor baron; squire and two other retainers (they double as wives))
A Dragonborn (fire/psi) Sorcerer got kind of jealous of wizards, and their familiars.
So when his affiliation required he get wiz-initiate to get particular Detective usable spells he realized something.. with his intelligence was almost as wickedly good as his charisma.. . HE
He dipped directly into a wizard and got a fey Bat Familiar as well.
Then naming it Bug-eater after the childhood pet of Missy Tia his cook and half tribal human and half cave folk (cliff-dwellers) second wife.

He as a noble wiz of course got an Unseen servant.. and discovered the disadvantage of an unseen servant is others is running into it and dropping the 1hp.
So they gave it a very short cheesecloth kimono (1lb cloth).. in the Lord's house colors. 
 He calls his retainers his crew (3),
 his unseen and tiny servants his horde (1+7), and..
TADA.. his flock of 
(oh.. did I tell you he got a position of reserve sergeant in the guard of the palace of the four winds 'Celestial warlock' under Bahamut )
Celestial Owls his choir (5). 
seven tools, five owls, a bat, and the Lord magic-user directly in combat. the unseen servant helping otherwise.. and the retainers staying out of such issues.. 

Quote from TheGunShoj >>

Is there a way to favorite this page so I can easily return to it?

 I'd reccomend just bookmarking it on your computer

I keep seeing that mentioned, but how do you actually do it?

Edit: Nevermind, I found it in the Extras.

For my halfling Arcane Trickster, I'm using an Elf Owl for his familiar. It's the smallest species of owl. For a small-sized AT, it seems perfect. The fact that it's called an Elf Owl makes it even better. Look it up on google.

Quote from belfastbiker >>

Apart from casting longstrider and mage armor on it to give it an AC of 14 and speed of 70ft, or perhaps frostbite / poison spray / restrain on the most dangerous mob, how on earth are wizard keeping these things alive?  I mean it's gonna be taken out first, surely?  With the lack of opportunity attack, how practically are peoply providing the help action?  Obviously fly to near the bad guy, distract, and fly behind someone or something I take it, exploiting cover bonuses?

https://www.dndbeyond.com/compendium/rules/phb/combat#Cover

 If you have a reliable frontline character, it won't get targeted as much.  By the way, it's an owl, how threatening can it be? (from the enemy's perspective)  Obviously, you and your fellow adventurers pose a greater danger than the little owl.  

Quick Question, because the Owl has advantage wouldn't it actually have an 18 passive perception?

Either this or the spider are the best familiar. With this, you have the perfect scout, it's easy to cheese combat, ya look cool, you'll never have to worry about seeing in the dark, and you have advantage on perception checks that rely on hearing or sight. Definitely pretty pog.

Quote from GrayroseJay >>

Quick Question, because the Owl has advantage wouldn't it actually have an 18 passive perception?

While seeing & hearing are the majority of Perception checks, it doesn't have advantage on all Perception checks, so no.  But it would be reasonable to rule that for passives that the advantage does apply to.

can you cast spells through an owl familiar?

So, a quick run down of literally everything I know about the usefulness of this creature and Find Familiar, as well as a few quality of life things:

If you go to the spells part of this site, and you're obsessively searching for touch spells to use, then you can sort by range by clicking the arrows beside "range/area", which is right above the spells, and right below advanced filters; I say this specifically because the devs didn't add an easy filter for range (pls fix devs)

Because of the owl's fly speed and ability to act as a whole other unit on the battle field, with touch spells to boot, as well as its flyby ability, it's basically living action economy cheese; simply ready your action to have fly boi cast a touch spell of your choice on his turn, and then immediately have him either fly over to somewhere safe on his turn, which honestly can simply just be higher up, or use the help action to, well, help. By the way, because it wasn't spelled out very clearly, you have an action, you have a bonus action if something specifically says you can use it as one, and you can use your reaction at pretty much any time (and if you use the Ready action, you use a reaction to do whatever you're readying), once again assuming you have something that specifically allows it (see the shield spell for an example).

Since familiars are entirely independent, and they have ridiculous darkvision and perception, they can essentially act as a living sentry while your party sleeps.

(for DMs specifically) Don't be a d*ck and target the familiar without a reason because it's annoying; reward your players for being creative and adapt to the situation in a reasonable way that doesn't ruin the experience because it isn't what you planned.

If you want to add this to your character sheet, or any familiar for that matter, go to extras (an option on that big ass square that has "actions, spells," etc, at the very end), click the "manage extras" button to the right of the searchbar, and there should be an add extras option that pops up; you then should click "choose a category," find the Familiar option, and you can search for the familiar that you want in the searchbar. There's an add button that pops up to the right of its name, and you can click it to have it in the extras thing there, you'll know it when you see it.

Per RAW (rules as written), your owl can use any action other than attack, which includes the help action; this was confirmed by one of the creators themselves, I believe, and although it's overpowered to all hell, it's how the rules are written.

The owl in specific has some really nice wisdom and dexterity stats, and nice bonuses in perception and stealth; because of the familiar's nature, you can use these to great benefit, in whatever situations you need.

(for both DM and player, and not pertaining to familiars) owls are said to live in both arctic and forest biomes; some forget this, so make sure to have them be in both places, if the circumstance comes up. Also, for owls irl, even owls not built to survive in the snow do so incredibly well, and there's a case I heard about of one surviving a freezer; they also have the ability to glide completely silently, due to cool physics things. Little known fact, they often prey on eagles, and are true terrors of the night for literally anything they think they can kill, and are unfortunately not very smart, using most of their brain's power for sensory processes; however, this is only because their environment didn't demand intelligence, simply because of the effectiveness and boosted survival rate of being a night-time predator, and an incredibly effective and stealthy one at that. 

Sadly no. However, if you use Chrome, you can bookmark it, or just write down the link to the page somewhere that you can either manually type it in or copy-paste it. The link is literally just dndbeyond.com/monsters/owl so it wouldn't even be that hard to memorize it, as I have.

i love owels

The owl is a great familiar with flyby, but people are misinterpreting the help action. Help is on a enemy target, not on a particular player character, and it's for the 'next' attack that targets the enemy, you can't specify whos attack gets advantage.

So if the owl goes at 10 and does help against a orc, the fighter goes at 9 and the wizard goes on 8, the fighter gets the advantage from the help action, not the wizard. Unless you ready actions there's no way around that. And you can't both do the help and move as a readied action so the owl ends up in a vulnerable position. 

So, to clarify how combat familiar owl works:

You ready a touch spell, with the condition of release being something that gives your owl the ability to release that spell on an opponent, or for example, "my owl gets within touching range of an enemy." It's important to note that, so long as your spell is readied, you're technically concentrating, which leaves you vulnerable. I would personally capitalize on that 100 ft range, and use all my movement to get as far away from enemies or close as possible to another party member that can protect you for the rest of your turn.

Once it's your owl's turn, you have them fly over to an enemy. When they trigger your Ready, you cast the spell as a Reaction, which obviously does sacrifice that reaction (taking out the opportunity for valuable spells, so beware), but nonetheless, the spell is delivered through your owl. 

This, however, doesn't end the owl's turn. Assuming you have movement left, you can have your owl safely retreat, maybe even back to you, with its extended range of movement. Additionally, because it has Flyby, it doesn't trigger an attack of opportunity, meaning that your little destroyer of action economy flies without possibility of harm (assuming your DM isn't evil and your enemies don't Ready their action to shoot it out of the sky at any time).

Now, aside from combat, familiars are incredibly powerful. I recommend checking out this document of things I meticulously collected for a fair few creative uses, a few cool spells you can use (abuse, more like it), and another iteration of how to use them in combat from a different person.

The Help action, for clarification.

I would argue that a turn represents 6 seconds and everyone is actually doing things simultaneously during the same 6 seconds.  We just have initiative to avoid chaos during a battle.  The owl should be able to fly in, take the help action, and then use the rest of it's movement speed to fly away, thus using flyby.  Since your player is technically doing things at the same time, flyby is still valid as a help action, giving the next player who engages with the enemy advantage. 

Jeremy Crawford, the last word on anything D&D says, 

The Help action doesn't say you must stay next to a foe you're distracting, so you don't have to stay next to it for the action to work #DnD https://t.co/74YhWl5UH6