The earth's magnetic field causes a compass to point north, as compasses are powered by magnets. The magnets inside compasses are drawn to the magnetic North Pole, which is about 1,000 miles south of the actual North Pole. Therefore, even though a compass always points north, it does not always point toward the true north.
Magnets operate on the principle of poles. The north pull of one magnet is drawn to the south pull of another magnet. Although the earth's magnet North Pole is in the north, in regard to the magnetic pull of compasses, it actually acts as a South Pole because it pulls the north ends of magnets.