From Bulbapedia, the community-driven Pokémon encyclopedia.
Ability symbol SUM-onwards
Ability (Japanese: 特性 ability) is a special mechanics in the Pokémon Trading Card Game, named after the analogous element in the main series games. It may be held by any type of Pokémon cards
Abilities are additional effects that the card's player can trigger once or multiple times during their turn, before they attack, or that are always active during the game. For example: Keldeo-EX has an Ability that allows the player to switch Keldeo-EX with the Active Pokémon, once per turn; Alolan Muk has an Ability that blocks other Pokémon's Abilities and is active always, until Alolan Muk is no longer in play.
With the release of Black & White, Abilities replaced Pokémon Powers and their successors Poké-Powers and Poké-Bodies as well.
With the release of Sun & Moon, Ability symbol has been updated with a new one with red background and white text.
List of Abilities