What's with these files with a tilde (~) at the end?

[Dave M G]

Ubuntu Users,

    It seems that various programs, like Gedit and Quanta and others, 
when they edit text files, like regular text and HTML files, create 
these backup files that have a tilde character on the end. They look 
like this:
    examplefile.txt~

    These files don't show up when I view a directory in Gnome/Nautilus, 
nor when I run ls from a command prompt.

    But they show up when I browse directories in some applications, 
like gFTP or Amarok.

    These files are annoying because, say, in gFTP, after I've edited 
some HTML files, I have two of each one, and I have to ctrl+click every 
second file to send the real ones.

    Today I noticed when I selected in FireFox to download a file to my 
desktop, there were almost a dozen of these files there on the Desktop 
as viewed through FireFox, even though they don't show up on the Desktop 
itself.

    Why are these applications creating these files with tildes at the 
end, how do I get rid of them, and can I stop them from being 
automatically created in the first place?

    Any advice would be much appreciated.

    Thank you.

--
Dave M G