This diagram explains the rules of Rock, Paper, Scissors (or the version Rock, Paper, Scissors, Lizard, Spock).
The diagram shows that Rock beats Scissors,
Scissors beats Paper, and Paper beats Rock.
For the bonus version, Spock beats scissors and rock,
Lizard beats spock and paper,
Rock beats scissors and lizard,
Paper beats rock and spock,
Scissors beats Paper and lizard.