Stars in the Galaxy a lot, and remember all of them is impossible. People chose those who helped them find the path to farming. Then broke them into groups and joined the imaginary lines.
The names of stars and constellations got about 7 thousand years ago. The Egyptians, Greeks, Chinese, peoples living on the banks of the Indus and Euphrates, gave them the names of their gods, heroes and animals. The brightest and most significant stars have their own names: Sirius, the polar star and the other One of the first catalogues of the starry sky, "Almagest" of the Greek astronomer Ptolemy (137 ad), lists the 48 constellations and 1022 stars ancient Greek sky. This directory was used until the middle of the XIV century. These constellations are based mainly on the mythology of Ancient Greece and cover the area of sky accessible to observations from the South of Europe.
The seven brightest stars of the constellation URSA major form the shape similar to the bucket.
"Modern sky" has already 88 constellations. New constellations were introduced in the era of great geographical discoveries, in XVII-XVIII centuries in the course of exploring the southern sky and fill in the "blanks" in the Northern sky. The names of these constellations do not have mythological roots.
Now the constellation look differently than a hundred thousand years ago. Differently they will look in the future. View constellations changed for several reasons: they move across the sky, some stars disappear, others are born.