The most common way to create a magnet is by applying a magnetic field to a material that is capable of being magnetized. This process is called magnetization. When a magnetic field is applied, the magnetic domains within the material become aligned with the field. The strength of the magnet depends on the strength of the magnetic field and the material's ability to be magnetized.
Some materials, such as iron, nickel, and cobalt, are easily magnetized. These materials are called ferromagnetic. Other materials, such as aluminum and copper, are not easily magnetized. These materials are called paramagnetic.
The Earth is a giant magnet. The magnetic field of the Earth is caused by the movement of molten iron in the Earth's core. The magnetic field of the Earth protects us from harmful solar radiation.