Polo is a horseback ball game, a traditional field sport and one of the world's oldest known team sports. The game is played by two opposing teams with the objective of scoring using a long-handled wooden mallet to hit a small hard ball through the opposing team's goal. Each team has four mounted riders, and the game usually lasts one to two hours, divided into periods called "chukkas".

Two mounted umpires accompany the players, (four on each team in outdoor polo, three on each team in arena polo) and a third man sits near the middle of the field to referee in case of a questionable call between the mounted umpires. At the end of the chukker, the players change horses.

More Info: vapolo.org