I have recently started packaging a bash script of mine into a .deb file so that I can upload it to my PPA, and I have noticed a lot of talk about a file which seems to have been created from my source code or something called <packagename>_<versionnumber>.orig.tar.xz (<packagename> replaced by the name of the package that I am using dh-make to package, and <versionnumber> replaced by the version number). I have also noticed that a folder called debian with lots of files in it has been created, and I have been following some official Debian guides to edit the files.
But I still don't really understand what this .orig.tar.xz file is, what its purpose is, and how it is used with this debian folder. Could anyone explain this to me?