A magnet is any object that produces its own magnetic field. The magnet strength of these objects can vary from imperceptibly weak fields to incredibly strong fields, depending on a number of characteristics. Magnets can be classed into two distinct groups: permanent magnets and electromagnets, and non-magnets can be defined as either ferromagnetic, paramagnetic, or diamagnetic. Ferromagnetic materials like iron are strongly attracted to magnets, paramagnetic materials like aluminum are only slightly attracted to magnets, and diamagnetic materials like carbon are weakly repelled by magnets.
Permanent magnets are those objects that are magnetized and will stay magnetized forever. One can make a permanent magnet by taking a hard ferromagnetic substance, like hard iron, lodestone, cobalt, and a number of rare earth metals, and magnetizing it strongly. Soft ferromagnetic substances may gain a temporary magnetic field, but will tend to lose it rather quickly. Electromagnets, on the other hand, consist of coils of wire that gain a magnetic field when electricity is run through it, but lose it immediately when the electricity ceases.
