This are the mod Quake virtual machine (QVM) files.
Unpack the zip into your quake 3 arena folder, then select the mod on the mods menu.
This files are manadatory to play the mod and can be used with any quake 3 arena variation.
This is a tweaked quake 3 arena executable (EXE).
Unpack it into your quake 3 arena folder, then run that executable instead of the normal one.
This file is not mandatory to play the mod, but will enhance your enjoyment with numerous tweaks.
You can also use the executable with other qvm mods due to increased security, stability and features.