"Jurassic" was a period of history named for the Jura Mountains that border France and Switzerland - the place where rocks of this age were first studied. (This link depicting the Jura Mountains will permit you to zoom in.)
It was a time, paleontologists believe, BEFORE Tyrannosaurus rex (the biggest predator ever to stalk the American West) and one of its favored prey, the Triceratops. Both species likely lived during the Cretaceous Period.
What was the world like during the Jurassic Period? What kinds of dinosaurs lived then?
The answers to those questions may surprise you.