The concept of reviving teammates in Battle Royale games isn't new unto itself, nor is the concept new to online multiplayer shooters.
What is new, however, is the concept of respawning completely dead teammates — "Apex Legends" enables just that.
As is now standard in squad-based shooters, players on the losing end of a fight are "downed" initially. Thus begins a timer that leads to that player eventually dying, called the "bleeding out" process. If you get to your squadmate before they bleed out, you can revive them — pretty standard.
But if they die, a new timer begins. You now have about one minute to retrieve your squadmate's banner, which was left on their corpse. If you retrieve it safely, there are respawn stations where you can outright respawn a fallen teammate.
This may sound small, but it fundamentally changes the nature of Battle Royale games.
If you encounter a player and you kill them, but don't wipe out their whole squad, you risk allowing that player to be revived. Similarly, if you're killed early in the match, you shouldn't quit out of the game and move on — your squadmates are just as likely to revive you.
In so many words, it adds another layer of depth to the Battle Royale formula.
Anecdotally, the first game I won was a game where I was respawned by a savvy teammate who carefully got away at the right moment.