Regional variant

Regional Variant is a concept introduced in Generation VII. Some kinds of species of Pokemon had immigrated to another region a long time ago from their original region, and this caused them to change their appearnce and their type due to the change of their habitat. These Pokemon with different appearnce and type, however, only live in the region they migrated.

Alola Form
These Pokemon with special form are exclusive to Alola, thus they're called "Alola Form".