Constellation, also known as Burj in Arabic and Urdu is the area of sky. You can think sky as World and Countries as Constellations. Countries have divided world into several regions. In the same way, constellations have divided the whole sky in 88 pieces. Out of these 88 constellations, 12 are Zodiac constellations. This means that the Sun appears to be in these 12 constellations for 12 months. Each month the Sun changes its constellation and moves to another and in total passes from all 12 constellations of the zodiac.
You surely have heard people saying, “My sign is Scorpio, mine is Gemini, his sign is Virgo, this in reality means that when that person was born, the Sun was passing through the Constellation of Scorpio”.
Out of all these 88 constellations, 48 were defined by Ptolemy 150 CE and 40 were defined by numerous scientists after 1603 CE.
The constellations mainly are named on the characters of Greek mythological stories. They are named after animals, persons, instruments etc.
Every night, Greek mythologies pass from overheads. Orion the Hunter faces Taurus the Bull, Scorpio the Scorpion goes to Orion the Hunter to negotiate with him and later kill him. Constellations are just human imagination. Long ago when people didn’t have any other activity, they used these stars as symbols and project their stories on the sky. You may find that constellations don’t exactly match the names they carry because they are just human imagination and not a work of nature.