NHL lines refer to the various combinations of players on the ice during a game, typically organized into forward and defensive units. Each team usually employs four forward lines and three defensive pairings, allowing for strategic matchups against opponents. Coaches adjust these lines based on player performance, matchups, and game situations, aiming to optimize scoring opportunities and defensive stability. The chemistry between players on a line can significantly impact a team's success, making line management a crucial aspect of NHL coaching.