Ballet is a type of dancing performed for theater audiences. Like other dances ballet tells us a story, expresses a mood or simply reflects the music. Ballet dancers perform many movements that are unnatural for the body but when these movements are well executed, they look natural.
Ballet Techniques

A turnout is when dancers rotate the legs in the hip sockets as far to the side as possible. Its an unnatural position in which the thigh bones are rotated sideways. It is very hard to get this perfect.
Another technique is an Arabesque. This is done by extending the back leg straight behind and pointing the foot. If the knee is bent, it is called an attitude. In either pose the leg on the ground may be bent or straight.

The beginnings of ballet can be traced to Italy in the 1400's at the time of the Renaissance. The Italian dukes competed with one another in giving costly fancy entertainment that included ballet dance performance. The dancers were noblemen and noblewoman of a dukes court who danced to please their ruler and to stir the admiration and envy of his rivals.
The Romantic Period - Most of the ballets told stories taken from ancient Greek myths or dramas. But during the 1800's, people no longer cared about gods or heroes. This period began as people became interested in stories of escape from the real world to dreamlike worlds or foreign lands. The Italian choreographer Flippo Taglioni created the first romantic ballet in 1832 for his daughter Marie Taglioni. In this period male dancers became chiefly porters, whose purpose was to lift the ballerinas.

There are many famous ballets. A very popular one is "Swan Lake." It featured Margot Fonteyn and Rudolf Nureyev. Another one is "The Clowns." One that everyone knows is "The Nutcracker." Two of the very famous ballet dancers are Vaslav Nijinsky and Anna Pavlova. In 1907 they did a ballet called "Le Pavillion d'Armide" Vaslav played a slave and Anna played a heroine, Armide.

The purpose for ballet is more for entertainment. Also ballet hasn't vanished like other dances. Its been around since the 1400's and people are still dancing today.