When I use the GUI text editor and I open the /etc file, I have the file /etc/xinetd.conf and the file /etc/xinetd.conf~. However, when I browse throught the file system, there is no file /etc/xinetd.conf~. Why is this?
You usually never directly edit a file. The editor usually edits a copy of the original and then writes over the original with each "save".
The Linux vi editor edits a copy with the ".smp" extension. Windows based programs such as "Microsoft Word" edit a copy with the "~" at the begiining of the filename.
This "~" you are seeing is probably a temporary file. It will disappear once you exit the eitor.