This is the core item that makes up any Pokémon game. The Poké ball items are used to capture wild Pokémon and tame them to become your own. They are a very common object and almost every Poké stop will drop at least 2 or 3 balls to add to your inventory. If you run out, more can be purchased from the in game store using real money. If you walk around enough you should be able to obtain enough balls so that you will never need to pay for them.
How To Capture Pokémon
When you travel around the world, you will encounter new Pokémon to capture. When you click on the Pokémon that pops up, you will begin a battle. You will need to throw a perfect shot that hits the Pokémon on the head. This will usually cause the Pokémon to get captured inside the Poké ball. Some of the stronger Pokémon can break out of the ball and you will need to throw multiple balls in order to capture them.