Magnetic domain

A magnetic domain is like a tiny magnet inside something that is made of metal. All magnets have two sides, one that attracts things and one that pushes them away. The same is true for a magnetic domain, except that each side of the domain is made up of lots of tiny magnets all arranged together in the same direction thanks to the metal it's inside of. Because all the tiny magnets are pointing the same way, it creates one big powerful magnet. This can be useful for producing electricity or for holding things in place, like in a refrigerator magnet.