There is no single-player goal or plot in this game.
Quake III Arena is one of the first first person shooter games, which don't support any software rendering any more. A hardware accelerated [graphics controller]? is mandantory to run the program.
Like its predecessors Quake and Quake II it can be heavily modified to support other gaming styles. Quake III Arena can use (like Quake II) native [shared libraries]? to store the game code but the preferred method is to program all modifications in pure ANSI-C and compile them with a special version of the free C compiler LCC? into machine independend [byte code]?, which will be interpreted by an in-game virtual machine. The virtual machine in Quake III Arena even uses "[just in time]?" techiques like modern Java virtual machines.