Jazz in its current form has a lot of different dance ideas all rolled into one form.  There are up-beat jazz movements, more soft/graceful movements, movements on the floor, exciting tricks, and movements of pure joy. Jazz came into fruition from African slaves in the United States as a much needed outlet of expression.  It was then popularized by Vaudeville acts of the early 20th century and greats such as Katherine Dunham and Bob Fosse.  It has continued to evolve into the style we see today.