In navigation, the word bearing is used for different methods that try to find out the angle between an object used for this purpose, and a reference direction. There are different systems of reference that can be used for this. A system of reference that is commonly used is that of Cardinal directions, as they can be found with a compass. The direction a ship is pointed can also be the reference.
Points that can easily be determined, and that move very little, can be taken as reference. Such points include stars, mountains, the sun, and beacons. Beacons come in the form of lighthouses on the coast, but also as electric beacons or other sea marks on the open sea.
Bearings can be measured different ways. Optical bearings rely on visual information, other systems rely on radar for tools.