Rugby is a contact team sport played between two teams of 15 players each on a rectangular field. It originated from soccer and was the origin of American football. Players can only move the ball by running, kicking, or throwing it sideways. Points are scored by grounding the ball in the try zone or by kicking field goals. The game is made up of two continuous 40-minute halves with rolling substitutions and only stops for injuries or penalties. Positions include forwards like props, hookers, and flankers in the scrums and lineouts and backs like scrum halves, centers, and wings that handle the ball.