Eevee can have eight evolutionary forms in the Pokémon games.
These forms are Vaporeon, Jolteon, Flareon, Espeon, Umbreon, Leafeon, Glaceon, and Sylveon. Fans commonly call them Eeveelutions. Each represents a different Pokémon type and is reached through different conditions or items.
The first three forms—Vaporeon, Jolteon, and Flareon—appeared with Eevee in Pokémon Red and Blue. Espeon and Umbreon arrived in Pokémon Gold and Silver, while Leafeon and Glaceon debuted in Pokémon Diamond and Pearl. Sylveon was introduced in Pokémon X and Y.
Eevee itself is a Normal-type Pokémon known as the Evolution Pokémon. Its branching evolution design is unusual because most Pokémon species have a much narrower evolutionary path. A planned ninth form was reportedly considered for Pokémon Sun and Moon but was not included in the released games.