A cvar is a game defined variable that stores a value.
A complete list, A to Z, can be found here... cvar list for dod:s..... UPDATED condump date July 2010
The previous cvar list that was there was taken on 30 July 2006... it has been replaced.
To get a list like this you type "cvarlist a" in the console... that will get you all commands, values and their description for that letter... in this case "a".
Do the same for the rest of the alphabet. Don't do too many at one time, they get "cut off" when doing a condump.
Type "condump" after that and a text file is saved named "condump000" in the dod folder.
A command and it's value can be entered in the console or placed in the users config files or used in scripts. This changes many aspects of the game, from audio volume, video, physics... lots of things. There are currently 1761, (that I know of anyway) in DoD:S.
I will not attempt to list and explain them all, most of them have no huge benefit while you are playing the game... some are interesting. These are the ones I will add as I find them.
You can help too, if you find some info use the dodbits forums, make a thread and I will add the information here :)