From IFWiki

The traditional style of navigation between rooms, which uses a set of absolute directions. Typically, these are the cardinal directions (N, S, E, W), intercardinals (NE, SE, NW, SW), UP and DOWN, and, less consistently, IN and OUT. Shipboard directional systems employing PORT, STARBOARD, AFT, FORWARD, etc. are usually considered equivalent.

Most IF uses this system, which relies upon the convention that the player-character has an infallible sense of direction, regardless of orientation in the game world. (For alternatives, see navigation).

See also: compass rose.