In ballet, the corps de ballet is the group of dancers who are not principal dancers or soloists. They are a permanent part of the ballet company and often work as a backdrop for the principal dancers
In this scene from Swan Lake, the corps de ballet is forming a "V" at the front of the stage. They are directing attention to the principal dancer in the spotlight. The dancers behind her are also corps de ballet and form a backdrop.
This 1877 Edgar Degas painting, Ballet at the Paris Opéra, features not only the soloist but the corps de ballet.