Medals

Medals are achievements earned by reaching milestones for distance walked, PokéStops visited, Pokémon caught, and other gameplay achievements. Each medal has three achievement milestones: bronze, silver, and gold. Some achievement milestones unlock rewards - such as an increased chance of successfully catching certain Pokémon type.

Levels
They have three different levels with various requirements on how many times a task needs to be performed.

Milestone medals

 * † The Ace Trainer medal was obtainable by training Pokémon in team-owned Gyms. Training was removed during the Gym rework and it's not longer obtainable, however the medal is still present in game—keeping the progress before the Gym rework.

Bonuses
Type medals grants you:


 * +1 catch bonus for Bronze Medal.png Bronze Medal
 * +1 catch bonus for Silver Medal.png Silver Medal (+2 catch bonus total)
 * +1 catch bonus for Gold Medal.png Gold Medal (+3 catch bonus total)

This counts only for capturing Pokémon with type corresponding to the medal. (The Dragon Tamer medal grants a bonus for catching Dragon-type Pokémon etc.) If a Pokémon has two types, the game will average the catch bonus you have for those two types.