It evolves from Mareep starting from level 15, and evolves into Ampharos starting at level 30.
Its fleece quality changes to generate strong static electricity with a small amount of wool. The bare, slick parts of its hide are shielded against electricity.
(From Bulbapedia )
Flaaffy is a pink, bipedal, sheep-like Pokémon. Its white mane of wool curls sideways on the top of its head and extends to its torso. Flaaffy's ears are thick cones with black stripes, and it has small, blue eyes. It has stubby arms and one nail on each foot. Flaaffy's long tail has black stripes and is tipped with a blue orb.
Storing too much electricity caused Flaaffy to lose the wool over most of its body, but the bare, rubbery skin protects it from the electricity stored in its fleece. The quality of Flaaffy's fleece can change to generate more electricity with less wool. The orb will light up when Flaaffy's mane is fully charged, and it can attack by firing electrifying hairs at opponents. One is most likely to find Flaaffy in grassy meadows and fields.
(From Bulbapedia) Flaaffy is based on a sheep with patchy wool. Its type and Ability come from how wool builds up static charges. Its evolutionary family may also have been based on the title of the science fiction novel Do Androids Dream of Electric Sheep?.
(From Bulbapedia) Flaaffy may be a combination of fluffy and baa (the sound sheep make). Aa may also be a reference to a double-A battery, given Flaaffy's Electric type.