Surely the name of this program, Fives and Threes, tells you nothing. It is a little ambiguous, but it is an entertaining domino game where you can play with up to four players at once, or just you against the PC.
The aim of Fives and Threes is the same as the usual dominos, meaning you have to get rid of all your pieces before your opponent. It is interesting that Fives and Threes is very configurable, letting the user select the colours, sounds, etc.
Fives and Threes also has its own chat, to send messages to the other players and keep up conversations while you play.