Dragons are a combination of all the things humans find scariest. They are big beasts, But also snakes, But also (sometimes) BREATHE fire, Or come from the unknown depths of the ocean, And they are often very smart and tricky.
They can represent many things from strength to wisdom to courage to GODS. But to me they represent how somethings are universal to all humanity, Because they show up in so many different cultures.
Dinosaurs are just ancient chickens.