Difference between Energy Type and Energy Cost
Energy is the resource system in the Pokémon TCG used to power attacks and abilities. In the top right corner of the Pokémon card is an energy symbol. This is the Pokémon's energy type. The energy type influences weakness and resistance, as well as the type of energy cost. The energy costs, to the left of the attacks and abilities, determine how much energy and which type of energy (e.g., Fire or Psychic) is needed. Most of the time, the required energy type is the same as the Pokémon's energy type. Often, it is also a combination of the energy type and the Colorless energy type. For Colorless Pokémon and attacks with Colorless energy costs, any type of energy card can be used, and the later-introduced Colorless energy card can be used as any type of energy card accordingly. Retreat is usually also possible with a Colorless, i.e., a freely selectable, energy type.
Evolution of Energy Types
Initially, there were Grass, Fire, Water, Lightning, Psychic, Fighting, and Colorless types, and corresponding energy cards (except for Colorless). Later, Metal and Darkness were added, and finally Fairy, which was removed again with Sword & Shield. Since the Dragon Selection / Dragons Exalted expansions, the Dragon type has also existed in the trading card game. Since it does not have its own energy card type, it uses combinations of other energies.
Types in the Video Game
As in the TCG, types in the video game determine Pokémon's weaknesses and resistances. Attacks are also assigned a specific type, which does not have to be the same as the Pokémon's type. Compared to the trading card game, there are more types in the games (e.g., Rock, Ghost, and Poison) and some are named differently (Colorless is Normal, Darkness is Dark, and Metal is Steel). Since there are fewer types in the TCG, there are different approximations as to which type a non-existent one is assigned (e.g., Flying is Colorless, Ground and Rock are Fighting, and Ice is Water). Poison was initially counted as Grass, then Psychic, and then Darkness over time. Except for the time when Fairy was its own type, its assignment there is Psychic.
