Magnetism, a fundamental force of nature, is primarily explained through two key concepts: the domain theory and the atomic theory.

The atomic theory delves into the microscopic origins of magnetism, stating that it arises from electrons orbiting the nucleus of atoms and spinning on their axis, which creates tiny magnetic fields. While most electrons are paired with opposite spins, effectively canceling out their magnetic effects, atoms with unpaired electrons, such as iron atoms, produce a net magnetic field, acting as mini-magnets. This movement of electrons and their spin is considered a fundamental property that gives rise to an atom's magnetic behavior.

Building upon this, the domain theory illustrates how groups of atoms form magnetic domains, which are like tiny, self-contained magnets with their own north and south poles. In an unmagnetized material, these domains are randomly oriented, causing their collective magnetic fields to cancel each other out, resulting in no overall magnetism. However, when a material is magnetized, for instance by an external magnetic field or by stroking it systematically with a magnet, these domains align in the same direction, creating a strong, overall magnetic field. The more domains that align in the same direction, the stronger the overall magnetic field.

The interaction between magnets is governed by their poles: opposite poles attract, while like poles repel. When a magnet is broken, it simply creates smaller magnets, each still possessing both a north and south pole. Conversely, a material can be demagnetized by heating it to a high temperature (above its Curie point) or by forceful impact, which randomizes the direction of its magnetic domains.

The overview also differentiates between various forms of magnetism, including ferromagnetism (strong attraction in materials like iron, cobalt, and nickel), paramagnetism (weak attraction due to unpaired electrons), and diamagnetism (weak repulsion caused by changes in electron orbits). Electromagnets, unlike permanent magnets, produce magnetic fields only when an electric current flows through them.

The Earth itself behaves as a giant magnet, with a magnetic field extending into space that protects the planet from solar radiation and cosmic rays. Magnetism has numerous applications, ranging from electric motors and magnetic storage to medical imaging (MRI). Common magnetic materials include ferrites (ceramic magnets), alnico magnets, neodymium magnets, and samarium cobalt magnets.