Spring MVC Controller: what are difference between "return forward", "return redirect" and "return jsp file"

I don't understand what I should use. I have two pages - intro.jsp(1) and booksList.jsp(2). For each page I created one Controller Class. The first page has button which opens second page:

<form method="GET" action="/request-list">
        <input type="submit"/>
</form>

The first question is: I am not sure about correctness this button. It works well, but I have question mark after press this button.

The second question is: When I press that button, method with next annotation is called (Controller for the second page):

@RequestMapping(value = "/books")
@Controller
public class BooksListController {

   @RequestMapping
   public String booksList() {
      return "jsp/books/booksList";
   }
}

What should I return by this method? In other words how can I jump from first page to second one?

1. return "redirect:/books"; returns http://localhost:8080/books?


2. return "jsp/books/booksList"; returns http://localhost:8080/request-list?


3. return "forward:/books"; returns http://localhost:8080/request-list?

I see that result is the same: all these Strings gave me the same page (page 2 was opened). In which cases I should use "redirect", "forward", "page.jsp"?

Also I've read Post/Redirect/Get article. Do I have to use "redirect" after POST method handling??