Hockey is played with 3-4 definitive positions: forwards (centres and wingers), defencemen and goalies. However, it wasn’t always like this. In the early days of the sport and even in the early days of the NHL, the roles (outside of goalie) were more fluid.
And, more importantly, rosters were tiny, often as small as seven players before the pro-leagues got going: a goalie plus three forwards, a point player, a “cover point” player (one or both of these could also be “rovers”), and a reserve/substitute in case someone got injured. Once the pro-leagues matured, the rosters crept up to 10 or so players. The star players would often play two-thirds of a hockey game (whereas, now, star defencemen play a third or slightly more, and star forwards often play less than a third).