Relative Bearing is the direction to an object from a ship, expressed in relation to the heading of one's own ship.
Units of Measure
This was expressed either in degrees or in compass points.
Relative bearings in degrees might be expressed in the range -179 to 180 (0 being dead ahead, and 90 being directly to starboard), or in the range 0 to 180, with a qualifying prefix of "red" for objects to port and "green" for starboard, e.g., "Train guns Green 50".
Relative bearings in compass points would generally be expressed with "to port" or "to starboard", e.g., "Enemy 3 points to port". Sometimes, the direction would be relative not to the bow but to other cardinal point (most often a beam), e.g., "Enemy 2 points abaft the port beam."