The tutorial is pretty good, but it boils down to betting how many dies of a certain number are on the board (this includes your opponents). Bets must go up, either with the number on the dice or the number of dice, or both. During your turn, you can either enter a new bet, call a bluff (if you don't believe the last bet), or declare the last bet spot on.
When a bluff is called, if it was a bluff, the bluffer looses a die; if there were at least that number of dies showing the bet number, the caller looses a die. When a bluff is declared spot on, if it is, everyone but the declarer looses a die; if not, the declarer looses a die.
The object of the game is to be the last player with dice.