Final answer:
A compass is an instrument that uses the Earth's magnetic field for heading information and can be used for navigation or computations in certain systems. It aligns with the Earth's magnetic field and points towards the magnetic north pole.
Step-by-step explanation:
A compass is considered as any system or instrument which uses the Earth's magnetic field as its primary source of heading information. It can be employed as a navigational aid, computer input for weapons delivery systems, or magnetic variation computations in inertial navigation. A compass consists of a small metal needle that is magnetized and free to turn in any direction, allowing it to align with the Earth's magnetic field and point towards the magnetic north pole.