Constellation
A constellation is a named pattern of stars and the official region of sky around it; astronomers recognize 88 constellations covering the whole sky.
Definition
A constellation is a group of stars that people imagined as a picture, such as a hunter, a bear, or a lion, named long ago by cultures around the world to help remember the sky. Today the International Astronomical Union recognizes $88$ constellations, defined in 1922 with exact boundaries that tile the entire celestial sphere, so every star belongs to exactly one; which constellations are visible depends on the season, the time of night, and the observer's latitude. The boundaries follow lines of right ascension and declination, and the patterns are line-of-sight projections of stars at very different distances that slowly deform over tens of thousands of years through proper motion. Precession of Earth's axis, with a period of about $26{,}000$ years, gradually shifts which constellations mark the solstices and equinoxes.
Example
Orion the Hunter is easy to find on winter nights by the three bright stars of his belt, and the Big Dipper is part of Ursa Major, the Great Bear. From Charlotte at about $35^\circ$ north latitude, Orion is high in the evening sky in January but hidden behind the Sun in July, while Ursa Major never sets because it lies close to the north celestial pole. In Orion, Betelgeuse is about $550$ light-years away, Rigel about $860$, and the belt stars roughly $1{,}200$ to $2{,}000$, so the hunter is a chance alignment spanning over $1{,}000$ light-years of depth.
Key Insight
The stars in a constellation are not really near each other; they only look close from Earth. Constellations change with the seasons because Earth revolves around the Sun, not because the stars move, and each night a given star rises about $4$ minutes earlier than the night before. Constellations remain useful as sky addresses: variable stars, supernovae, and exoplanets are named by their constellation, and the zodiac constellations mark the ecliptic, Earth's orbital plane projected onto the sky.