One of the main mechanics in Pokemon games is catching Pokemon. It is done by throwing any kind of Pokeball at a Pokemon and hoping it catches. Some Pokeballs are stronger than others, and the main pokeballs are Pokeballs, Greatballs, and Ultraballs, going from worst to best. Some Pokemon are harder to catch than others, but there are ways to make a Pokemon easier to catch. One is to get the Pokemon to as low health as possible. Then use a move to give it a status condition like paralysis and sleep. After that you can just keep throwing Pokeballs until you catch it.