The offensive zone, or attack zone, is the area on the ice behind the blue line where the opposing team's goaltender is located. The offensive zone reaches from the blue line to the end of the boards behind the opposing team's net.
Nearly all goals in the NHL are scored from within the offensive zone. In order for members of the attacking team to cross the blue line into the offensive zone, the puck must cross the blue line before any of the players, or else the whistle will be blown and play will be stopped due to an offside call. The goal of the players defending their zone is to get the puck out of the zone by passing it over the blue line and back into the neutral zone. This is also referred to as "clearing the puck". Once the puck is cleared, all attacking players must leave the offensive zone before the puck, and then the players, can re-enter the offensive zone.