A puck is a small, hard, flat disk used in ice hockey. Made of vulcanized rubber (a tough, bouncy material invented in the 1800s), a hockey puck is about three inches across and one inch thick, weighing roughly six ounces. Players use long sticks to shoot, pass, and slap the puck across the ice, trying to send it flying into the opposing team's goal.

The puck slides smoothly on ice but moves fast and can be dangerous: professional hockey pucks sometimes reach speeds over 100 miles per hour during slap shots. That's why hockey players wear so much protective gear, including helmets with face guards.

Hockey pucks are frozen before games to make them less bouncy and more controllable. A room-temperature puck would bounce unpredictably across the ice, turning the game into chaos. When you hear announcers talk about controlling the puck or winning the puck, they mean gaining possession of it during the fast-paced action.