Type is an attribute of a piece. Possible types are:
The type "player" can only be used once per game, for the player piece.
Treasure pieces are usually used as goals which the player must collect to advance the game, or they grant extra points.
World pieces are used for environment pieces such as platforms and decorations.
Enemy pieces work against the player and are used to make your game more challenging. But some may also be used as goals.
Keys are pieces that you must push into a lock to open it.
A lock blocks a path like a platform could, but if touch a lock with a key the lock will open!