How is an artificial magnet prepared from a natural magnet?

Artificial magnets are prepared from natural magnets by single touch method in the following manner :

Place the iron or steel bar on a table and take the natural magnet and stroke it along the length of the bar in one direction only from one end to the other. Now, Repeat this stroking motion 20–30 times to magnetize the bar. Bring a few iron pins near the bar. If they stick, the bar has become an artificial magnet.