Short answers, pulled from the story.
Jazz dance is a performance dance and style that arose in the United States in the early 20th century. It expands on African American vernacular styles of dance that arose with jazz music, tracing its roots back to African dance traditions. It may allude to vernacular jazz, Broadway, or dramatic jazz.
Vernacular jazz dance emerged from everyday life and cultural practices and incorporates ragtime moves, the Charleston, the Lindy hop, and mambo. Dramatic jazz dance was performed on the show stage and was promoted by Jack Cole, Bob Fosse, Eugene Louis Faccuito, and Gus Giordano.
The Charleston was named after the harbor city of Charleston, South Carolina. Its popularity surged in the 1920s following the 1923 song "The Charleston," composed by James P. Johnson for the Broadway show Runnin' Wild, and it reached its peak between 1926 and 1927.
Katherine Dunham was an anthropologist, choreographer, and pioneer in black theatrical dance who introduced isolations to jazz dance and created the Dunham technique. In 1944 she opened the K.D. School of Arts and Research in Isadora Duncan's former New York studio, followed by the Dunham School in 1945, where Marlon Brando and James Dean studied.
The Harlem Renaissance of the 1920s celebrated black art, literature, and music as jazz grew more popular and dance styles evolved from African traditions, social dances, and jazz music. It saw the rise of figures such as Josephine Baker and the Nicholas Brothers, who brought jazz dance to mainstream audiences.
Contemporary jazz became well known through television shows such as So You Think You Can Dance, while commercial jazz, popular since the 1980s, blends hip hop and jazz in the music videos of Janet Jackson and Paula Abdul. Latin jazz, developed and popularized by Maria Torres at Broadway Dance Center, appears in the films El Cantante and Dance with Me.