Which force explains why magnets attract or repel each other?

Magnetism is one part of electromagnetism. In everyday materials, it comes from the motion of electrons and their intrinsic spin, both of which are governed by electromagnetic interactions. That is why permanent magnets can attract iron, repel each other in certain orientations and power technologies ranging from motors to MRI scanners. James Clerk Maxwell unified electricity and magnetism in the 19th century, showing they are different aspects of one force. The same force also produces light.