I think the only thing we have in the Documentation area is
here (in case you haven't seen it). Maybe someone has something else.
Basically a widget zone is just a container that contains 0 or more widgets. You can also have multiple widget zones since BE 1.6. Most people have just one widget zone (with multiple widgets in it), but you can actually have multiple widget
zones -- giving each widget zone a unique ZoneName.
Widgets are in the /widgets/ folder. One folder for each widget. Ex: /widgets/MonthList, /widgets/Search, /widgets/TextBox.
A widget always has a widget.ascx file. This is what displays the widget. It'll also often have widget.ascx.cs too, to store code in. Most widgets (but not all) have an edit.ascx file. This is what is displayed when you click the
'Edit' link next to a widget to configure the widget. Similarly, if an edit.ascx exists, there will usually be an edit.ascx.cs file that contains the code.