How does Gnome populate its menus?

[J S <webnews comcast net>]

I've been using Gnome for a few years, but I recently wanted to learn a
little bit more about the guts of the system.  One thing I really want o
fiddle with is the Gnome menus.  Can somebody explain to me how gnome
populates it's menus?  I understand that there are .desktop files
describing the menu items and their actions.  What I don't get is how
gnome decides what directories to check to find these .desktop files. 
Is there a way to make gnome look into a user's home directory for more
.desktop files?  Is there a nice way to allow each user to customize
his/her menu structure?  I LOVE GNOME.  I've even been able to convert
my wife from a Windows environment to Gnome.  But, it sure seems easier
in Windows to customize a user's menu than it does in Gnome.  That
really hurts to say that.  Please help me figure out how Gnome does
this.  Maybe, if I have the time and motivation, I will try to put
together a little application that allows users to customize the menu
just as easily as they can in Windows.

Josh

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J S <webnews comcast net>