From Bulbapedia, the community-driven Pokémon encyclopedia.
A Contest Battle (Japanese: コンテストバトル Contest Battle) is an anime-exclusive Pokémon battle variation and the second round of a Pokémon Contest. These battles are different from regular battles in the sense that is not only the strength of the attack that matters, but also the style of its execution.
A Contest Battle is a five-minute battle where two Coordinators face each other while continuing to show off their Pokémon's talent and skill. During the battles, Coordinators are not allowed to substitute their Pokémon.
Contest Battles use a point system. Each Coordinator begins with a fixed number of points and the object of the battle is to decrease the opponent's points. Points are deducted by the competition jury, usually formed by Mr. Contesta, Mr. Sukizo and the resident Nurse Joy. Coordinators lose points when their Pokémon are hit by an attack, when their Pokémon's attack fails, when the opponent's Pokémon performs a particularly appealing move or combination, when the opponent's Pokémon uses their Pokémon's attack to its own advantage or when they receive a yellow card. Additionally, Coordinators can be disqualified upon being found cheating.
The winner of a Contest Battle is the one that has more points when time runs out, the one that reduced the opponent's points to zero, or, if a Pokémon fainted during the battle, the one with the remaining Pokémon. If there is a tie at the end of five minutes, the battle goes into Sudden Death, which is an extension of the battle with no time limit. The Sudden Death ends when a Coordinator runs out of points or when a Coordinator's Pokémon is knocked out.
A Contest Battle scoreboard
The Double Battle format is also used in Contest Battles. Battles following this format were first seen in the Hoenn Grand Festival and then again in the Kanto Grand Festival. Some Contests are held under the Double Performance rule, which means that Coordinators must use two Pokémon in all rounds of the competition. During a Double Battle, Coordinators have to be able to command two Pokémon at all times, presenting both Pokémon to look the best they can. Additionally, Contest combinations require the Pokémon using the moves to be in sync with one another.
In Hoenn and Kanto Contests, Coordinators do not seem to have a preference on whether they win by knocking out their opponents' Pokémon or by having more points at the end of a battle. In Sinnoh Contests, however, Coordinators seem to be hesitant about earning Ribbons by causing their opponents' Pokémon to faint, preferring to use the five minute time limit to show off their Pokémon's skills to the max and letting the Contest judges decide who gets the victory.