Pikachu is classified as an Electric-type Pokémon in the main series.
Its design and abilities are built around electricity: Pikachu stores electrical energy in red cheek pouches and can release attacks such as Thunder Shock and Thunderbolt. Its lightning-shaped tail reinforces the electrical theme.
Pikachu first appeared in Pokémon Red and Green and became the franchise mascot largely through the anime. The anime’s producers selected Pikachu as Ash’s partner because it was visually distinctive, appealing to a broad audience, and not tied to a player’s choice among the three original starters.
Pikachu is often confused with Raichu, its evolution, or Pichu, its later-added pre-evolution. All three are associated with electricity, but Pikachu itself is the middle stage. In the original games, Pikachu evolves into Raichu when exposed to a Thunder Stone.