is an object that has a magnetic field. It can be in the form of a permanent magnet or an electromagnet. Permanent magnets do not rely upon outside influences to generate their field. They occur naturally in some rocks, but can also be manufactured. Electromagnets rely upon electric current to generate a magnetic field - when the current increases, so does the field.
Magnets are attracted to, or repelled by, other materials. A material that is strongly attracted to a magnet is said to have a high permeability. Examples of materials with very high permeability include iron and steel. Liquid oxygen is an example of something with a low permeability, and it is only weakly attracted to a magnetic field. Water has such a low permeability that it is actually slightly repelled by magnetic fields. Everything has a measurable permeability: people, gases, and even the vacuum of outer space.