Pokémon Gold and Silver/Poké Balls

Balls are items (but they have their own pocket in the bag) that you can catch Pokémon with. They are very vital to the game, because you will need it to catch Pokémon for your journey. It starts with Poké Ball, to Master Balls, which are very rare and will always catch any Pokémon.

Your first ball will be when you go back to Elm's Lab, (after seeing your rival) where his lowest assistant will walk over to you (like he did when you got a potion from him) and give you a Poké Ball. At one point the Radio Tower will be invaded by Team Rocket and you will have to beat all the Rocket people. After this, Elm will call you (Please confirm this, because it might be after you beat Claire, the last Johto Gym Leader) and say something and tells you to come to his lab. When you talk to Elm, he will give you the Master Ball.