Amateur hockey is governed by two major associations, Hockey Canada and USA Hockey. The International Ice Hockey Federation (IIHF) rules are used in professional and amateur leagues. The National Hockey League (NHL) governs the rules of the professional teams. This is where most of the North American professional leagues derive their rules.
Hockey is a game of three twenty-minute periods with the time running only when the puck is in play. The teams change goals at the beginning of the second and third periods. A tie is broken by a "sudden death" period. A team has no more than six player on the ice at one time. The players can be removed for different periods of time for actions such as tripping charging, or spearing which are a two-minute penalties. Five-minute penalties are for fighting or doing the other penalty actions with an intent to injure. A ten-minute penalty is incurred for unsportsmanlike conduct or when a player incurs two five-minute penalties in one game. When a player is out on penalty, the team is short that player until the penalty time is over. This may put the opposing team in the "power play" position where they have a full team of players while the other is at a disadvantage.
The game begins with a face off between two players at the center line. Each team tries to shoot their puck into the opponent's goal and score. Players cannot commit an offsides which means the player is preceding the puck over the opponents blue line. If this occurs they must do another face off. The players may also not shoot a two-line pass where a player passes the puck from his offending zone to a teammate beyond the center line. This results in another face off. Iceing occurs when the team in possession of the puck shoots it behind the goal line but not in the goal, and a member of the opposing team touches it first. This again results in a face off. The players are allowed penalty shots if they are impeded from behind when in possession of the puck with no player between them and the goal except for the goalie. That player is allowed one shot at the goal with only the presence of the opposing goalie. Hockey games can be low on scoring, but never on excitement.