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.
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.
In Hoenn and Kanto contests, Coordinators seem to have no qualms about winning a battle round by knocking out the opponent's Pokémon. For example, in Weekend Warrior, May won both the preliminary and the final battle rounds by knocking out her opponent's Pokémon, not by having more points at the end of the five minute time limit.
However, in Sinnoh contests, Coordinators seem more hesitant about earning ribbons by simply besting the opponent in battle. In Yes in Dee Dee, It's Dawn!, Dawn was even disappointed about having won a battle round by causing her opponent's Pokémon to faint.