Six players are on the ice for each NHL team during normal play: five skaters and one goaltender.
The five skaters are normally three forwards—left wing, center, and right wing—and two defensemen. Teams constantly replace these players in line changes, often sending out a coordinated forward line and defensive pair to keep players fresh during the fast-paced game.
The number six describes players actually participating, not the entire team roster. An NHL club can dress up to 20 players for a game, typically including 18 skaters and two goaltenders, but only six from each side can be on the ice at full strength.
Penalties change the usual matchup. A minor penalty commonly creates a five-on-four power play, meaning one team has four skaters and the other has five, with each still normally using a goaltender. Overtime uses fewer skaters, so the familiar six-player figure applies to standard even-strength regulation play.