A constellation is a group of stars, which seem to be forming different figures, letters, etc. at night. This term has come from the Latin words con, which means together, and Stella, which means star. The ancient Babylonians, the Greeks and the Romans gave the names of their kings, queens, heroes and animals to these constellations.
Some of the later found constellations were given the names of scientific instruments such as the Sextant, the Compass and the Microscope. Today, the astronomers recognize 88 constellations in the sky. It is not easy to make out in the sky the figures that suggested the early names. For example, Aquilla is the eagle, Canis Major and Canis Minor are the big and little dogs, but the constellations do not look like these figures.
All the constellations cannot be seen from one place or at the same period of the year. At different places and in different seasons we can see different constellations.
Below Constellation info from Wikipedia (Read More):-
In modern astronomy, constellation refers to an area of the celestial sphere, defined by exact boundaries. The term "constellation" can also be used loosely to refer to just the more prominent visible stars that seem to form a pattern in that area.
In colloquial usage, a constellation is what astronomers call an asterism: a group of celestial bodies (usually stars) that appear to form a pattern in the sky or appear visibly related to each other. Examples are Orion (which appears like a human figure with a belt, often referred to as "The Hunter"), Leo (which contains bright stars that outline the form of a lion), Scorpius (which can seem reminiscent of a scorpion), and Crux (a cross).
http://en.wikipedia.org/wiki/Constellation
