What does hysteresis loop represent?

Hint :In order to solve this question, we are going to first define what the process of hysteresis is. After that we will be analyzing what the hysteresis loop is and what its significance is, and what we can conclude from the hysteresis loop of a ferromagnetic material obtained after magnetization.

Complete Step By Step Answer:
A ferromagnetic material is magnetized by applying the magnetic field around it, up to a point when the field is increased, the magnetization also increases this process is termed as Magnetization. After a point, it starts to reverse back and the magnetization starts to decrease to a point when it becomes zero. This process is termed as Demagnetization and after a point it again starts to increase.
This whole process of magnetization and Demagnetization is known as Hysteresis. Now the area enclosed by the hysteresis loop represents the loss of energy per unit volume of the material per unit cycle when a unit volume of the magnetic material is carried through one reversal of the magnetization.

In other words, the hysteresis loop represents a closed curve obtained by plotting the magnetic flux density $ B $ of a ferromagnetic material against the corresponding magnetizing field $ H $ when the material is taken through a complete magnetizing cycle.

Note :
The area of the hysteresis loop measures the amount of energy that is basically lost per cycle of magnetization. The area of the hysteresis curve for steel is more than that of soft iron. The magnetic materials whose B-H curve is more are useful for making permanent magnets. The retentivity i.e. the retention of the magnetism is more.