Technically, they are the same garment. Dinner Suit is the traditional British/Australian term, while Tuxedo is the American term. However, in the current market, "Tuxedo" is becoming the dominant search term. For your wedding invitations, "Black Tie" is the correct code to indicate that men should wear this garment (black/midnight blue jacket with satin lapels, bow tie, and satin-striped trousers).