Overtime in hockey, like in any sport, is a period of time used to determine the winner of a game that is tied at the end of regulation time. Hockey overtime falls under the category of "sudden death," meaning that the first team to score wins, but there are some variations. During the National Hockey League regular season, tied games are followed by a five-minute overtime period. The overtime period is played four-on-four, whereas regulation play features five players per side.
If neither team scores during the five-minute overtime, the teams engage in a "shootout." In the shootout, each team selects three players to take what is essentially a penalty shot - a one-on-one play between one player and the other team's goalie. The teams alternate shots in the shootout, and the team with the most goals out of the three attempts is the winner. Should the teams remain tied after the three rounds of the shootout, extra rounds are added until the tie is broken. Shootouts are often used in international play as well, though international shootouts usually consist of five rounds instead of three.
In the NHL postseason - the Stanley Cup playoffs - shootouts are not used, but ties cannot be allowed. If a game is tied at the end of regulation, the teams play a standard 20-minute period of overtime. It's still sudden death, but the period is longer. If the teams remain tied after the first overtime, there is an intermission similar to those between regulation periods, and the teams resume play with another 20-minute overtime period. This continues until one team scores.
Because scoring is relatively infrequent in hockey, this style of overtime can make for some extremely long games. The longest game in NHL history was a playoff game between the Detroit Red Wings and Montreal Maroons in 1936, which Detroit won 1-0 after more than 116 minutes of overtime - or nearly six full overtime periods. The six overtimes equate to two full regulation games, all played after the three regulation periods.
Fourteen times, the Stanley Cup Finals have ended on an overtime goal. The most recent was in 2000, when New Jersey's Jason Arnott scored on Dallas goalie Ed Belfour in the second overtime of Game 6 to give the Devils the Stanley Cup.