nah it's the high. Indica is when you smoke and your mind is fucked like you go like a zombie and can't get off the couch AKA couchlock and it's like you just had a stroke or something.

Sativa is a celebral high, really upbeat, like you just tooted some rock and feels like you can run around energetically.

Its genetics, Indicas are from middle east and afghans and sativas are found in tropical areas (wild plants)