There could be an entire encyclopedia of Jazz, but for Folkipedia, it just needs to be set in context.
Jazz is another American music form that originated with the Black African Americans as did Ragtime. It appears to be a fusion of manydifferent styles and influences from both Europe and Africa including syncopation, blue notes and call and response. Jazz also relies heavily on improvisation.
There are two main forms of Jazz. Traditional (Trad Jazz which is Dixieland - When the Saints) and the non-traditional which covers many genres.