If you throw a Poké Ball at a mob and successfully capture it, you can level it up by having it kill other mobs. If a mob tamed by the pokeball dies, it'll be returned to the pokeball.
If you throw a Poké Ball at a mob and successfully capture it, you can level it up by having it kill other mobs. If a mob tamed by the pokeball dies, it'll be returned to the pokeball.