Magnetism refers to the phenomena associated with magnets, which are materials that produce a magnetic field that affects other materials and objects in their vicinity. Magnetism can be observed at both the macroscopic and microscopic level, and it is intimately related to the flow of electric charge.

The magnetic properties of materials can be understood in terms of the behavior of their atoms and subatomic particles. In particular, the electrons in an atom generate a magnetic field due to their intrinsic spin and orbital motion. When a material contains a large number of atoms with aligned magnetic fields, it exhibits a net magnetic behavior.

There are several types of magnets, including permanent magnets, which retain their magnetic properties without an external magnetic field; temporary magnets, which only exhibit magnetism when exposed to a magnetic field; and electromagnets, which are created by running an electric current through a coil of wire.

Some of the key applications of magnetism include data storage (in hard disks), medical imaging (such as MRI), power generation (in generators), transportation (such as maglev trains), and many others.