The International Astronomical Union recognizes 88 official constellations. Forty-eight of the 88 constellations were described by the ancient Greeks. Constellations are not the same as asterisms, which are simply recognizable patterns of stars such as the Big Dipper.
Constellations are identified by their Latin names, which are abbreviated using three letters recognized by astronomers. The stars that make up constellations actually have two names, their official names as well as the names that denote their relation to the constellation to which they belong. For example, the star Betelgeuse belongs to the constellation Orion and is given the name Alpha Orionis.
These "star pictures" do not represent physical groupings of stars, meaning that the stars that make up constellations do not lie physically close to one another in space. Rather, the stars in constellations appear to make patterns when they are observed from Earth.