How a ferromagnetic substance is a magnet is outlined in a series of steps starting with a moving electric charge is surrounded by a magnetic field. A magnetic field is produced by the motions of an electric charge. The electric charge motion is produced by electrons rotating around the nucleus and spinning on their axis. Each produces a tiny electric field which produces a tiny magnetic field. Non magnetic substances have equal electrons spinning in opposite directions, their magnetic fields cancel out.
The theory of magnetic domains is introduced based on the magnetic field produced by spinning electrons.