You are probably most familiar with magnets as providing a way to stick things to the refrigerator and the file cabinet. Iron and steel are so ubiquitous that we get the impression that magnets stick to everything, whereas in reality they are attracted to only one common material.
Magnets also have a more important role than this. The magnetic force can be controlled electrically, and thus is one force that is fairly large, acts over a visible distance, and which we can turn on and off at will. This will be the subject of the next section. Still another way that we use magnets is in information storage. Your credit cards, floppy disks, and the hard disk in your computer remember the information we entrust to them in the form of a pattern of magnetization -- that is, many little regions that are magnets pointing one way or another.
Although most iron and steel objects don't seem to be magnets -- they don't spontaneously collect paper clips -- this is only because they consist of many small regions that are magnetized in random directions. An external magnet induces order into these, which may persist after the magnet has been removed. Materials differ in the extent to which this happens; the memory effect is enhanced if the magnetic particles are in the form of needles that are all aligned the same way.