Substances are magnetized when their electrons spin in the same direction. What this does is it creates charge differences in a substance.
Magnets have north and south poles. These poles dictate the direction in which the magnetic field flows both inside and outside of a magnet. On the outside, field lines flow north to south; inside they flow south to north.
Interestingly enough, magnets will always have both a north and a south pole. This can be observed if a magnet is cut in half. Since the poles are the result of the flow of field lines, and the field lines always form loops, there cannot be magnetic monopoles. In other words, there can't be a north pole without a south pole, and vice versa.
The magnetic field created by magnets can be utilized to exert forces on other objects. A common application of the magnet is the electromagnet.