In Voodoo, the spirits are called Loa. There are thousands of Loa in Voodoo. Although there is cosiderable variation among families and regions, there are generally two groups of Loa, the Rada and the Petro. The Rada spirits are mostly seen as "sweet Loa," while the Petro are seen as "bitter," because they are more demanding of their "children." Rada spirits appear to be of African origin, while Petro spirits are of Haïtian origins. Each loa has their own symbol called vèvè.