What are the domains of a ferromagnet?

The domains of a ferromagnet are small, localized regions within the material where the magnetic moments of atoms are aligned in the same direction, resulting in a net magnetic moment. Each domain is typically a few micrometers in size and can be thought of as a mini-magnet. In an unmagnetized ferromagnet, these domains are randomly oriented, canceling each other out. When the material is magnetized, the domains can grow or align in one direction, leading to an overall magnetic field.