The geographic north and south poles indicate the points where the earth's rotation axis intercepts earth's surface. Consider holding a tennis ball between your thumb and forefinger and pushing on the side to make it spin. The points where your thumb and finger make contact are the geographic north and south poles of the tennis ball's spin. A person standing on the equator is moving the fastest due to earth's rotation, while a person standing on a geographic pole does not move at all from earth's rotation. Earth's magnetic poles designate the central location of the region where the magnetic fields lines start and finish. 

Earth's geographic and magnetic poles are not exactly aligned because they arise from different mechanisms. Earth's magnetic field is caused by circulating currents of liquid iron in the outer core. Furthermore, earth's magnetic poles are constantly changing location relative to earth's geographic poles. 

Currently, the magnetic south pole lies about ten degrees distant from the geographic north pole, and sits in the Arctic Ocean north of Alaska. The north end on a compass therefore currently points roughly towards Alaska and not exactly towards geographic north.