A circumpolar star is so close to one of Earth's two poles that instead of rising and setting like other stars, it seems only to revolve around one point in the sky. This effect is caused by Earth's rotation on its axis and can be seen at high latitudes.
As Earth turns at a rate of one complete revolution per 24-hour day, celestial objects seem to rise over the eastern horizon, pass across the sky and set in the west. Near the poles, however, this motion has a different effect. An object over either the North or South Pole seems to describe a circle in the sky overhead with the center of the apparent orbit being the north or south celestial pole.