These are list files.
The list files here simply describe what files are contained in each Debian ISO image, in order to help users find which images they might want to download. They are simply text files, compressed to save space and download time.
For convenience for some users, this unofficial alternative build includes non-free firmware for extra support for some awkward hardware.
See the Debian CD FAQ for lots more information about Debian CDs and installation.
The images here were put together by the Debian CD team , using debian-cd and other software.