Which version do I need?
That depends on hardware for example if you have a bleeding edge video card it may only work with the latest version of Debian.
If you have very old PC you might need an older version of Debian.
If your restoring an old install of LinuxCNC 2.7 you might want Debian 9.
If you have a Mesa 7i96S you have to use LinuxCNC Uspace 2.8.4 or LinuxCNC Uspace 2.9 Febuary 24, 2022 or newer!
LinuxCNC Uspace 2.9 only runs on an OS that has Python 3.x so that means Debian 10 or newer.
A DEB package is an archive containing all the files including the compiled version of the applications, source codes, configuration files, images, and installation commands.