what is the theory and concept behind magnetic moment?? how do we explain it???

In general, the magnetic moment is the property of a magnet that interacts with an applied field to give it a mechanical movement. Hence, it is a quantity that determines the torque it will experience in an external magnetic field.

 

This concept arises in accordance with the torque that is applicable to a system where two forces act on it in opposite directions (torque on a tap). Similarly, the magnet having two poles will have a magnetic moment associated with it which will give rise to a torque.