Because Polaris is so near to the Pole, you can easily determine your approximate latitude by measuring the altitude of Polaris above the North Horizon Point. That is, Polaris hangs above the North Horizon Point, which entitles Polaris to be known as the North Star. Notice that Polaris lies at the end of the handle of the Little Dipper, Ursa Minor. Another way of designating Polaris is by the name -Ursae Minoris. You can find more about how stars are named in this interesting short article from Sky Publishing Company on star names .
Sidereal time is time told by the stars, rather than by the sun.
Sidereal time differs from solar time, because the stars maintain fixed positions on the Celestial Sphere through the course of the year, while the sun appears to move around the Ecliptic . Thus the stars and sun do not maintain a fixed relationship on the Celestial Sphere, and consequently neither does solar time in relation to sidereal time. A clock keeping sidereal time does not run at the same rate as a clock keeping standard time. The clock keeping sidereal time runs faster, because a sidereal day is 3 minutes 56 seconds shorter than a solar day. For the purposes of exams, you can take the difference to be about 4 minutes.