I'd aslo suggest you check the entries for
Application Framework and
Web Application Framework in wikipedia.
The answer to your question about what will happen if we don't use frameworks is: The seas will dry up, the stars will fall from the skies, and the world as we know it will end.
Just kidding
Actually, you don't have to use frameworks if you don't want to. However, in any application, particularly web applications, things can get messy and hard to maintain if there isn't some kind of organizing principle to the application. I use frameworks because I prefer not to reinvent the wheel by coming up with my own organizing principles (essentially inventing my own framework) and use principles created by smart people who have thought about the problem more than I have.
