Pokémon battles are a major part of Pokémon gameplay. They are turn based battles between Pokémon. The player can have up to six Pokémon who can enter the battle one or two at a time (depending on the type of battle). Each Pokémon has up to 4 abilities, which must be used to reduce the opponent Pokémon HP, either to 0 when they faint, or when they are weak enough to be captured by a pokéball. The player can switch to one of the other six Pokémon at any time, but will lose a turn. After a battle, EXP is divided equally between all Pokémon who took part, regardless of the part they played in the battle. This EXP will lead to Pokémon leveling up and learning new, more effective abilities.
Against Wild Pokémon
Pokémon battles can be against wild Pokémon, which are initiated by random encounters while walking through long grass. These Battles are always one-on-one battles in all Pokémon games, apart from the recent Diamond & Pearl, which introduced two-on-two battles against wild Pokémon. The enemy Pokémon cannot switch out for another Pokémon, and have limited access to items.
After a wild Pokémon has been weakened significantly, the player can use a pokéball to capture the wild Pokémon. If the capture is successful, the Pokémon will be added to the players collection, either directly, if the player has less than six pokémon in his party, or it will be sent to one of your Pokémon storage boxes if you currently have six Pokémon in your party.
Against Trainers/Gym Leaders
Pokémon battles can also be against other Non Player Characters in the game. Some characters will approach you if you enter their line of sight, others you must approach yourself. Pokémon Ruby and Saphire introduced two-on-two battles against trainers, which have also appeared in all its sequels. The Trainer can have up to 6 Pokémon and can switch to any of their available Pokémon at any time. He/She can also use items. The player cannot capture another trainer's Pokémon.