I have no idea what this is from but It looks amazing

It's part of the updates that were made to some of the Critical Role homebrew classes that were already on DDB. 

It's quite a nice spell; it's two levels higher than Fly, but adds defence against grappling, restraint and paralysis, plus a teleport to safety reaction that ends the spell. This means you can basically "nope" any spell with a limited range (where 60 feet can take you beyond that limit) or can take you out of almost every area of effect spell (you might still be on the edge of Circle of Death, Otiluke's Freezing Sphere, and it's unlikely you can get beyond Storm of Vengeance and similar).

I find quite interesting the possibility that you could use this feature to prevent yourself from being Counterspelled, since that has a limited range enough to trigger the failure, but the spell wouldn't affect the spell that you originally cast (that someone was trying to counterspell).

This is very powerful.  You are essentiallly immune to melee attacks, and a 60-ft. teleporting distance will help you evade the bulk of a wizard's arsenal.  Many spells have a range of 60 feet or less, some 120 feet.  Wait, there's also a flying speed?  Resistance to grapples and restraints?  Melee brutes will be unhappy.  If you take this as an archer ranger or sorcerer, you can easily dodge ranged attacks and spells just as well as melee attacks.  You would already be fairly far away from the enemy, so a 60-ft. teleport would take you even farther, possibly out of range.  Edit:  I don't think you'll get out of range of an archer though.  What are your ways of handling teleporting out of an archer's normal range, but staying within the archer's long range?  Should the enemy archer reroll with disadvantage?  What are your thoughts?  Still, in a cramped dungeon, you won't be able to escape a longbow that easily.  That could be helpful in avoiding a dragon's breath or a naga's poison spit.  This might be one of my new favorite spells.  Except on OoTOS paladins, its somewhat redundant, as they get immunity to grapples and restraints.  With this spell, you can still get grappled, its just must harder for creatures to grapple you.  Nonetheless, its still useful.     

The Aura of Open Seas Paladin's applies while in water, it's not applicable beyond it.

Edit: nevermind. I forgot the Tal'Dorei Reborn book updated the aura to be applicable universally.

Quote from Haravikk >>

It's quite a nice spell; it's two levels higher than Fly, but adds defence against grappling, restraint and paralysis, plus a teleport to safety reaction that ends the spell. This means you can basically "nope" any spell with a limited range (where 60 feet can take you beyond that limit) or can take you out of almost every area of effect spell (you might still be on the edge of Circle of Death, Otiluke's Freezing Sphere, and it's unlikely you can get beyond Storm of Vengeance and similar).

I find quite interesting the possibility that you could use this feature to prevent yourself from being Counterspelled, since that has a limited range enough to trigger the failure, but the spell wouldn't affect the spell that you originally cast (that someone was trying to counterspell).

 1. I'm afraid this might be a dumb question. If it's an action to cast the spell, wouldn't you already be in the air before someone attempts to grapple or restrain you etc? Or are you saying that someone may have grappled you before you turn and a an action you can fly away after getting advantage on breaking out of the grappling? I feel like I'm misunderstanding the mechanics somehow because if someone grapples you, you can also just misty step away without having to roll even with advantage. Please tell me this is the same mechanic.

2. The second part reads: When you are targeted by a spell or attack while this spell is in effect, you can use a reaction to teleport up to 60 feet to an unoccupied space you can see. If this movement takes you out of range of the triggering spell or attack, you are unaffected by it. This spell then ends when you reappear.

2. So it looks like you can be in the air for 10 minutes (the duration of the spell). So you could be anywhere and someone attacks you with a weapon or a spell, and then you use a reaction to teleport up to 60 feet to an unoccupied space you can see.If that takes you out of the range of the triggered attack, you're unaffected by it. So far so good. I get all that. Then it says the spell ends when you reappear. That's the part that has me so confused. When I reappear?  I feel stupid but what exactly does that mean? I react to a spell or attack and transport 60 feet away and hopefully out of the range of attack. But then the spell ends because I've "reappeared." Does that just mean that I've reappeared on the ground? If so, I feel stupid for asking but like I said, I need to know these things when I try to use this spell. 

3. I think that if I cast a spell in the air, and it's counterspelled, that would definitely be avoidable. I hope.That would be fantastic.

Thanks for any answers.

1. Your example is a good one. Someone grapples you before this spell is cast, once cast you have advantage to escape and fly away. Or you've already cast it, are now flying in the air and something grapples you in the air.

2. The spell ends when you use the teleport feature. So once you reappear, which is immediately after using the teleport, you lose your fly speed and all other benefits. If you choose to teleport to a space in the air, you are now falling. So its best to plan ahead and be within 60 ft of a space you could safely teleport to.

3. I believe counter spell does not target a creature, therefore the trigger to teleport "when you are targeted by a spell or attack" does not apply. So RAW you couldn't avoid a counter spell with this feature, although I can definitely see many DMs allowing it.

Thanks for your answer.

You said : "The spell ends when you use the teleport feature"  

But the way it reads is that it ends when you reappear. If you're 60 feet away, why not move in another direction entirely? The spell lasts 10 minutes so it seems reasonable you could move up to 60 feet in another direction. Say you're trying to escape the Mummy Lord. You react by teleporting 60 feet away. The spell only ends when you reappear. Why return to the mummy lord? Why wouldn't you just move in some other direction or with less than 60 feet so you're out of reach?  I'm not trying to be obstinate, I'm just trying to understand it.