At the root of jazz is the blues, the folk music of former African slaves in the U.S. South and their descendants, heavily influenced by West African cultural and musical traditions, that evolved as black musicians migrated to the cities. According to Pulitzer Prize-winning African American composer and classical and jazz trumpet virtuoso Wynton Marsalis:

Jazz is a musical art form originally developed by African Americans from around the turn of the 20th century. It is characterized by blue notes, syncopation, swing, call and response, polyrhythms, and improvisation.After originating in African American communities near the beginning of the 20th century, jazz gained international popularity by the 1920s. Since then, jazz has had a profoundly pervasive influence on other musical styles worldwide. Today, various jazz styles continue to evolve. As the first original art form to emerge from the United States of America, jazz has been described as "America's Classical Music".

Jazz has roots in the cultural and musical expression of West Africa and the western Sahel, and in African American music traditions, including blues and ragtime, as well as European military band music.

Jazz is unique in the way it utilizes previously unheard-of chord tensions. The Major7 chord (1 3 5 7) became a defining sound for Jazz, much in the way that the Dominant7 chord (1 3 5 b7) is associated with Blues. The most common tensions include the 9 and the 13.

The word jazz itself is rooted in American slang, probably of sexual origin, although various alternative derivations have been suggested.