Mentors are specially selected cats, chosen to teach an apprentice skills. Warriors, Medicine Cats, Deputies, and Leaders can be mentors. Mentors give their apprentice tasks, such as cleaning the Elders nests, or hunting for extra prey. Mentors teach their apprentices everything they know, and assess them on their skills.
Once the mentor believes their apprentice is ready to become a warrior (or full medicine cat), they perform a naming ceremony under StarClan's watch.