What does a hysteresis loop mean in the topic of magnets?

A four-quadrant diagram showing the magnetizing force relative to the resulting magnetization of a permanent magnet material as it is successively magnetized to its saturation point, then demagnetized, magnetized in the reverse polar direction, and finally remagnetized.
When the cycles are complete, this four quadrant graph will be a closed loop illustrating the magnetic properties of the magnetic material under test. Magnetically hard materials will have a larger area within the loop indicating the amount of magnetic energy. Magnetically soft materials lose their magnetism when the magnetizing field is removed and therefore have very small areas within the loop. The second quadrant within the four quadrants (+X and -Y) is the most important of the four curves and is called the demagnetization curve.