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
I'm not sure I'm following this paragraph. Is it exemplifying that Django admin can be complex in the sense that it can have a form with lots of fields?

In other words, what is "data" here? Above was "things passed to the form", but here it can now be displayed (I think I know what you mean, I'm trying to put it from the reader's perspective).