Soccer, also known as football, is played between two teams of 11 players on a large grass field with goals at each end. The objective is to score more goals than the opposing team by kicking or heading the ball into the opponent's goal. Soccer originated in England in the 19th century and is now the world's most popular sport. Key equipment includes a regulation size ball, uniforms, shin guards, and a properly sized field with goals and boundary lines. Games are officiated by referees who enforce the rules and signal fouls, out of bounds plays, and other decisions. Common fouls and their penalties are also described.