Checking or battling to retrieve the puck while in the offensive zone without possession of the puck. Because it takes place in the offensive zone, forechecking is almost exclusive to forwards.
Not all forwards are expected to be good forecheckers, but coaches expect all their forwards to make an effort to forecheck so that they try to retrieve the puck. The ability to forecheck well is something that all defensive forwards should have. For that reason, third and fourth line forwards are expected to be good forecheckers because they do not provide as much offensively as first or second line forwards.
When their team is defending, coaches usually choose to send one or two forwards to forecheck, depending on the situation of play. In a five on five situation, two forwards may be sent to forecheck, while the third forward and the two defencemen stay back in the neutral zone or defensive zone. If a team is shorthanded by one player, it may be safer to send only one forward to forecheck, so that if he is stuck in the offensive zone, the team still has enough players to defend against their opponent's attack.