A constellation is a group of stars that, when seen from Earth, form a pattern. The stars in the sky are divided into 88 constellations.
The brightest constellation is Crux (the Southern Cross). The constellation with the greatest number of visible stars in it is Centaurus (the Centaur - with 101 stars). The largest constellation is Hydra (The Water Snake) which extends over 3.158% of the sky.
There are also asterisms, smaller apparent star patterns within a constellation, like the Big Dipper (in Ursa Major), the Little Dipper (in Ursa Minor), Keystone (in Hercules), and the Pleiades (in Taurus).
The Big Dipper is a group of 7 stars (it is an asterism and not a constellation) contained in the Northern Hemisphere constellation Ursa major (The Great Bear).
Orion, also known as "The Hunter," is a constellation. The brightest stars in Orion are Rigel. Betelgeuse, and Bellatrix. The Horsehead Nebula and the nebulae M42 and M43 (called the Orion nebula) are also in this constellation.
Crux is the scientific name of the Southern Cross constellation. This well-known, cross-shaped Southern Hemisphere constellation is on the Australian flag. The brightest star in Crux is Acrux, a double-star system at the base of the cross. This constellation lies on the Milky Way and is surrounded by the constellation Centaurus on three sides. It is abbreviated Cru.
[Abbreviation: Sco] Scorpius (the scorpion) is a constellation of the zodiac. This constellation is seen along the ecliptic between Libra and Sagittarius. The brightest star in Scorpius is Antares, a red supergiant star that is about 500 light-years away from Earth and is about 230 times as big as the Sun. The second-brightest (Beta 1 Sco) is Graffias.