Xgrid is a way to connect computers to a server to do high calculations. You can use Apple's OS X Server GUI Programs, a shareware preference App(Forgot name), or the UNIX terminal on any Mac.
It works very similar to a networked system. There's agents(normal computers) that submits jobs to the controller(Main Computer System). The Controller could be a server or just one computer, once it's done doing a job for an agent, it sends data back and waits for the next job.
If you want to use xgird with the terminal type 'man xgrid' for all the details on commands.
Owner of GranitWorks
I'm not fully sure. I've only used firewire. Normally you want to use some type of gigbit fibre channel. I don't know if it works with ethernet or internet access if that's what your asking.
It's main purpose is for creating a cheap super computer for using software that can use Xgrid - like Maya or Mathmatic. Thats the big thing that I noticed. Unless you have Mac OS X server, you can only use Xgrid with Software that has been programmed for it.