The Trainer level (Japanese: トレーナーレベルTrainer level) is a property of the player in Pokémon GO. The player's Trainer level is increased by earning experience (abbreviated XP). Leveling up earns the player items, and certain levels unlock particular items. Once unlocked, items can appear when searching PokéStops.
After reaching level 5, the player can choose a team, which allows them to use Gyms.
The player can earn experience in the following ways:
A Pokémon ran away while catching it
Catch a Pokémon
Catch a new Pokémon
Catch the 100th Pokémon of 1 kind of Pokémon
Evolve a Pokémon
Hatch a 2 km Egg
Hatch a 5 km Egg
Hatch a 10 km Egg
Defeat a Pokémon in a Gym belonging to another team
Defeat all Pokémon in a Gym belonging to another team
Defeat a Pokémon in a Gym belonging to the player's team
(Added Prestige to the Gym) ÷ 10
Defeat all Pokémon in a Gym belonging to the player's team