I think that the question "What is jazz?” is a highly subjective one. Ask 100 different people "What is jazz?" and you're likely to get 100 different answers. But personally I think that jazz is American classical music. It is an American way of playing music which takes all of the unique elements of their culture. And no music that has been created in this country so exactly gives the ideals of individualism and gives one an opportunity to express oneself in such a special way as jazz does.
It's no secret that jazz music started in the black ghettos of New Orleans at the end of the 19th century. In the 1920s jazz moved up river to Chicago and New York. In the 1960s musicians began incorporating R&B, rock and new electric instruments into their jazz. Everything exploded and suddenly jazz was all over the place.
And at present, it seems that there are almost as many names for jazz as there are jazz groups. For example there are contemporary jazz, mainstream jazz, smooth jazz, alternative jazz, acid jazz, avant-garde jazz, Latin jazz, fusion, etc.
So perhaps a better question is: What do you like? From Jelly Roll Morton to Lee Morgan, from James P. Johnson to John Zorn, the answer is out there, preserved on record for our learning and listening pleasure. Yes, experiencing all the different styles of jazz is a daunting task, but the rewards are great; and the more you listen, the more you'll find similarities within the styles. What's more, jazz elements can be heard outside of its own genre - in rock, R&B, Latin music, African music - the list is endless.
Yet, one thing is sure: Jazz remains America's only original living art form. Today, its influence envelops the globe. It's expressive. It's enriching. Call it what you like - jazz is here to stay.