A stage in Pokémon is a level that a Pokémon has. All Pokémon have at least one stage, which is their basic form. Most Pokémon also have two other stages: an evolved form and a final form. The first and last forms of a given Pokémon are usually the most different from each other. For example, Pikachu's final form, Raichu, is much larger and has different proportions than its unevolved form.
Some Pokémon only have one stage (e.g., Weedle), while others have as many as five stages (e.g., Eevee).