Hi Neal,
It is simply an archive of different releases.
Sha1 refers to a cryptographic hash function. The sha1.asc file contains an sha1 string that is used to verify when the following command is run:
$ sha1sum
http://archive.cs.stedwards.edu/knop...N.iso.sha1.asc
that the output string corresponds to the contents (string) of the sha1.asc file. If it does not correspond, then most likely the download failed - i.e. experienced a communication problem that suffered a bit loss. Ditto similarly for md5sum and md5 files.
The cheatcodes allow you to do optional things, like freeing up the CD drive by issuing at the boot prompt:
boot: toram
which if you have enough RAM (~1GB) will allow you to load Knoppix into RAM without needing the Live CD to remain in the CD drive - i.e. it is free for other uses.
-- Tom