Fixed #22796 -- Added more basic explanations of forms

Now explains some more basic form handling before discussing Django;
simplifies initial examples; defers explanation of more advanced
aspects until later in the document
What I understood was that when a POST request submission is made by the browser, the server sends back some HTTP data, which the browser is waiting for, and no further URL needs to be fetched to get the result from the server (i.e. whatever the server's response is - an instruction to redirect, some HTML or whatever - it's pushed directly to the browser). 

On the other hand, when a form is submitted using GET, the browser obtains the server's response by fetching a new URL.

Is that incorrect, or just misleadingly expressed?