The North Star was given the name Polaris because it seems to sit directly above the North Pole. The North Star is fairly easy to find and has been used by mariners to help guide them for hundreds of years. The North Star is also the last star on the Little Dipper (Ursa Minor). It is the 40th brightest star in the sky and 2200 times brighter than the sun, it just doesn't seem as bright because it is so far away (430 light years from Earth). Polaris will remain the North Star until approximately 12000AD, at which time it be supplanted by Vega.
Polaris is simply the name for the star that is also called the North Star. It is located in the constellation that we (at least in America) call Ursa Minor or the Little Dipper. It is also in the Big Dipper -- Ursa Major.
Polaris is called the North Star or, also, the pole star. This is because of the fact that it appears to be pretty much directly above the North Pole. This means that it does not appear to move in the same way that most of the stars appear to move as the Earth rotates. Because of this, the star seems to stay still and is always in the North -- that is why it makes a good aid to finding directions.
Polaris as you have correctly pointed out is nothing else but the North Star. It was first noticed by the British astronomer William Herschel. It is called so because it appears to remain almost fixed exactly above the North Pole. It is the brightest star in the constellation Ursa Minor. Its of great use in navigation because its angle of elevation can be used to determine the latitude of a place. However, it can be seen only in the Northern hemisphere and cannot be used for navigation south of the Equator. It is a moderately bright star visible to the naked eye and lies about 430 light years from planet earth.
North Star (Polaris Star) is a star in the constellation Ursa Minor, being situated very close to the celestial north pole (declination 89°15'51"). Because of this, and because it is easily visible to naked eye (apparent magnitude 1.97), it is used for guidance, indicating with a pretty good accuracy (less than 1 °) the direction towards North.
Since the North Star does not fall below the horizon, it became a symbol of the Swedish royal maximum period of expansion of the kingdom, in the 17th and 18th centuries. North Star is depicted in relief with five points.