title: What does Provider in JAX-RS mean?
body: <p>Could anyone explain to me what a JAX-RS Provider is and what ‘@Provider’ annotation does? I have been reading documentation but I cant get it.<br>
  If there are resource classes that service the incoming requests, what do Providers do? How are they different from singleton resource classes when I create a persistent resource class (the one that is not per-request)? Or are those classes also providers?</p>