Game Played on Horseback with Mallets and a Ball: It's Polo

That's Polo.

Polo is a team sport where riders on horseback use long-handled mallets to drive a ball into the opposing goal. Played on a large grass field (300×160 yards), 4 players per side, divided into 7-minute periods called chukkers.

Variants: Arena Polo (3v3, enclosed), Snow Polo, Elephant/Camel/Yak Polo (exhibition), Bike Polo (urban, no horses).