Les Six (pronounced "Le sees") is French for "The Six". Les Six were a group of six French composers who were friends around the year 1920. They were young at the time, and they shared a lot of ideas about music. The composer Erik Satie called them "Les Nouveaux Jeunes", but then a man called Henri Collet called them "Les Six" in an article he was writing, and that name was always used for them after that.
In their music they tried to be different from Richard Wagner and other composers of Romantic music, and different from Debussy and Ravel who had been writing Impressionistic music. They also wanted to write in a simple way instead of using complicated rhythms such as those of Stravinsky or twelve tone music like Arnold Schoenberg. Many of their pieces were quite short. They liked strong, masculine music, especially jazz.
The six composers did not stay together for very long as they soon developed their own personal styles in their compositions.