During three 20-minute periods, teams battle up and down the ice trying to score by slapping a puck into their opponent's goal. A hockey player possesses the grace of a figure skater and the brawn of a boxer while working intricately with his teammates.
No more than six players per team are allowed on the ice at any one time. During the game, players may be swapped as often as the coach wishes, even during play. Professional players in North America are eligible but not usually available because of scheduling.
Made of vulcanized rubber. Weighs about 170 grams (6 oz.). The puck must cross the defensive blue line ahead of the first crossing offensive players. Otherwise, offsides is called resulting in a faceoff, where two players scramble for the puck dropped by the referee in the faceoff circle.
Source: Associated Press