Here is a list of all topics with brief descriptions:

Various root and pseudo-root Windows.	These are the various forms of root and almost-root windows that things on this Screen reside in
Screen masking window stuff	These are bits for a window that covers up everything on the screen during startup if we're showing the "Welcome window" splash screen
Various menus	These hold references to the various menus on the Screen
Various color definitions.	These define various colors we use for things on the screen
Various icon control bits.	Various configurations for how icons get displayed and laid out
Various cursors used on the screen.	These all come from the Cursors config var, or defaults
VScreen bits
Various graphics contexts	These are X Graphics Contexts, which are used for various sorts of drawing in X
Various font settings	Definitions of various fonts to use on the Screen
Window frame bits	These fields are related to the "frame" window; the decoration we put around the application's own window (the thing in TwmWindow.w above) to display borders, titlebars, etc