Dynamax
Dynamax is an ability that Pokémon can take with the item called the Dynamax Band. Trainers who obtain a Dynamax Band are able to Dynamax their Pokémon. Dynamax increases a Pokémon's size as well as their stats in battle, but can only be used once during a battle, and only for three turns. In addition, it can only be preformed in certain areas, such as special arenas in Pokémon Gyms.
All moves that a Pokémon knows will turn into Max Moves, which are more powerful than regular moves. The Max Moves that are learned are determined by the moves that the Pokémon knows.