What is permeability?
The ability of a material to become magnetized is called magnetic permeability. One example is rubbing iron against a magnet: the iron becomes magnetized and develops its own magnetic field, which means it has a certain degree of magnetic permeability. Many substances, including water, have some degree of magnetic permeability. When a material is placed in a magnetic field, it interacts with the field in one way or another. The permeability of a substance therefore describes the way in which the material responds and the effects of the field on the material. A substance with magnetic permeability will magnetize either in the direction of the field or opposite to it. So depending on its permeability, the substance will either be attracted to or repelled by the field.