You play against the dealerr. Here are the rules:

Rock beats Scissors
Scissors beats Paper
Paper beats Rock
First, choose a bet amount by clicking on the + and - buttons in the lower left corner of the screen. If you lose the game, you lose your bet amount. If it is a draw (both you and the computer make the same move), your bet is sent back to you. If you win the game, you are paid 1.9 times your bet. Good Deal Right! This game comes directly from Freemont Street in Las Vegas. Its just like playing in a real casino.

Winning Streak Bets:
You can also bet on a winning streak. To win the bet, you have to win many games in a row. Winning streak bets for 2, 3 or 4 matches are available. Choose one of them by clicking on the icon on the right hand side of the screen. You must win the corresponding number of matches in a row. Tie means you lose the bet. The payouts for winning streak bets are:

Winning Streak Payout
2 matches your bet x 8.7
3 matches your bet x 26
4 matches your bet x 78

The win streak bonus mode remains active until you click Quit Streak Bet .