Who Was St. Patrick, and Would He Drink Green Beer?

For Catholics, Episcopalians and some Lutherans, March 17 is the Feast Day of St. Patrick. For the rest of us, it's St. Patrick's Day — a midweek excuse to party until we're green in the face. But who was Patrick? Did he really drive the snakes out of Ireland or use the shamrock to explain the Trinity? Why should this fifth-century priest be remembered on this day?