Imagine this: creatures out of the wild that either have elemental powers or are just neat, living their best lives, and here come people with balls (we're talking some kind of scientifically engineered thing, not testicles) and they have the audacity to throw the balls at them. They can capture these cool guys inside these balls. What's it like in them, you might ask? No clue, I'm hoping it's just comfortable.
The goal is to capture as many of them as possible, and then you use them to fight other ones but it's supposed to be wholesome versus animal cruelty. That's it. That's the game.