A team's coaching staff is usually made up of one head coach, who is, in turn, assisted by one or several assistant coaches. Their role is obviously to lead the team before, during and after the game; they are in charge of setting up lines, changing them during the match, develop tactics, assign players special orders before or during the game as well as motivate their troops when they feel it is needed. They are also in charge of setting up training programs for their players so that they can develop and reach their full potential, in order to be at their best on the ice.
It is not uncommon, especially in lower-end leagues, to see veteran players take on coaching duties while still being on the active roster, most usually as assistant coaches and trainers but sometimes even as head coaches; we then talk of player coaches.