If we were to watch these over tens of thousands of years, we would see these clouds slowly drift apart, starting out like a cloud of gas and expanding to become thin strings of gas. These, too, come in many colors. Each star is given a number that represents its brightness as seen from the earth, as are all other objects in the night sky. This number is called its magnitude. Actually, there are two different measures of magnitude - apparant magnitude and absolute magnitude.
Apparant magnitude is how bright an object looks to an observer on Earth.
An object's apparant magnitude is dependent on it's absolue magnitude and it's distance from Earth. Therefore, a moderately bright star that is relatively close may look brighter than an extremely bright star at a long distance. The system of magnitudes is a strange one - a brighter star has a lower magnitude than a fainter one. Positions Stars have coordinates, just like a city. Of course, they have different names and different measurements.