Players of the games are designated as Pokémon Trainers, and in the main series Pokémon games, these trainers have two general goals. These are to complete the Pokédex by collecting all of the available Pokémon species found in the fictional region where that game takes place; and to train a team of powerful Pokémon from those they have caught to compete against teams owned by other Trainers, and eventually win the fictional Pokémon League. These themes of collecting, training, and battling are present in almost every version of the Pokémon franchise, including the video games, the anime and manga series, and the Pokémon Trading Card Game.
In most incarnations of the fictional Pokémon universe, a Trainer that encounters a wild Pokémon is able to capture that Pokémon by throwing a specially designed, mass-producible spherical tool called a Poké Ball at it. If the Pokémon is unable to escape the confines of the Poké Ball, it is officially considered to be under the ownership of that Trainer. Afterwards, it will obey whatever its new master commands, unless the Trainer demonstrates such a lack of experience that the Pokémon would rather act on its own accord. Trainers can send out any of their Pokémon to wage non-lethal battles against other Pokémon; if the opposing Pokémon is wild, the Trainer can capture that Pokémon with a Poké Ball, increasing his or her collection of creatures.
As a reward, the Trainer receives a Gym Badge, and once all eight badges are collected, that Trainer is eligible to challenge the region's Pokémon League, where four immensely talented trainers (referred to collectively as the "Elite Four") challenge the Trainer to four Pokémon battles in succession. If the trainer can overcome this gauntlet, he or she must then challenge the Regional Champion, the master Trainer who had previously defeated the Elite Four. Any Trainer who wins this last battle becomes the new champion.