Updated:
17 Feb 2022
Fighting against the Team go Rocket, defeating other Pokémon to get a Gym for your team, going to Raids… All of these things will demand a lot from your Pokémon. If you win or lose a battle, it doesn't matter, because your Pokémon will be damaged, and you will have to heal them, especially if your Pokémon faints and you expect to battle with that same Pokémon again.
How to heal fainted Pokémon
● Click on "items"
● Click on "Revive", which is a yellow item.
● Pick the Pokémon you want to revive, then click on another Potion to restore the rest of their Stamina.
● Another way to heal fainted Pokémon is to evolve them, and then proceed to restore their Stamina, using a Potion.