Originally Posted by ReaderAt2046
For that matter, even demons are not an Always Evil race, they're the evil portion of the angelic species. Or at least that's the way they are IRL, maybe D&D does things differently (though I'd prefer a different name in that case).
Must say that part killed me :)
How demons and angels and such are "IRL" highly depends on which religion/culture you draw your inspiration from, but to answer your indirect question, the devils of DnD are kinda fallen angels, demons are another breed all together, and the fight between angels and the demons is what lead to the devils falling.