Ice hockey is played on a hockey rink. During normal play, there are six players, including one goaltender, per side on the ice at any time, each of whom is on ice skates. The objective of the game is to score goals by shooting a hard vulcanized rubber disc, the puck, into the opponents goal net, which is placed at the opposite end of the rink. The players may control the puck using a long stick with a blade that is commonly curved at one end.
Players may also redirect the puck with any part of their bodies, subject to certain restrictions. Players can angle their feet so the puck can redirect into the net, but there can be no kicking motion. Players may not intentionally bat the puck into the net with their hands.
Hockey is an offside game, meaning that forward passes are allowed, unlike in rugby. Before the 1930s hockey was an onside game, meaning that only backward passes were allowed. The period of the onside game was the golden age of stick handling which was of prime importance in moving the game forward. With the arrival of offside rules, the forward pass transformed hockey into a truly team sport, where individual heroics diminished in importance relative to team play, which could now be coordinated over the entire surface of the ice as opposed to merely rearward players.
The five players other than the goaltender are typically divided into three forwards and two defencemen. The forward positions consist of a centre and two wingers a left wing and a right wing. Forwards often play together as units or lines, with the same three forwards always playing together. The defencemen usually stay together as a pair, but may change less frequently than the forwards. A substitution of an entire unit at once is called a line change. Teams typically employ alternate sets of forward lines and defensive pairings when shorthanded or on a power play. Substitutions are permitted at any time during the course of the game, although during a stoppage of play the home team is permitted the final change. When players are substituted during play, it is called changing on the fly. A new NHL rule added in the 2005 2006 season prevents a team from changing their line after they ice the puck.
The boards surrounding the ice help keep the puck in play and they can also be used as tools to play the puck. The referees, linesmen and the outsides of the goal are in play and do not cause a stoppage of the game when the puck or players are influenced by either bouncing or colliding into them. Play can be stopped if the goal is knocked out of position. Play often proceeds for minutes without interruption. When play is stopped, it is restarted with a faceoff. Two players face each other and an official drops the puck to the ice, where the two players attempt to gain control of the puck.
There are three major rules of play in ice hockey that limit the movement of the puck offside, icing, and the puck going out of play. The puck goes out of play whenever it goes past the perimeter of the ice rink onto the player benches, over the glass, or onto the protective netting above the glass and a stoppage of play should be called by the officials. It also does not matter if the puck comes back onto to the ice surface from those areas as the puck is considered dead once it leaves the perimeter of the rink.
Under IIHF rules, each team may carry a maximum of 20 players and two goaltenders on their roster. NHL rules restrict the total number of players per game to 18 twelve forwards and six defensemen plus two goaltenders