Hi Rae,
i think there is 9 species of basil. Each variety of basil can add an accent to a garden: dark opal offers stunning purple foliage and mauve flowers; the miniature or bush basil is especially attractive for borders; the ruffled varieties (O. basilicum 'PurpleRuffles' and O. basilicum 'Green RuMes') offer unique textures.
I found this article, there you can find more info about all species of basil and how to grow them:
http://www.e-calc.net/articles.php?tid=3455 Good luck!