Thai basil is sweet flavored, but has a hint of licorice taste to it. Thai basil has purple stems, and its leaves are narrower and perkier than its Italian cousin. Bury your nose in a bunch of Thai basil and you'll smell anise, not pesto. Flavorwise, it's spicier and bolder, too.
Thai basil stands up to cooking a little better than sweet basil, making it a good choice for soups, stir-fries, and curries. It can also be eaten raw sprinkled over salads or cold noodles dishes, and used interchangeably with sweet basils in most recipes.