"VNC (Virtual Network Computing) is a gift from AT&T Laboratories Cambridge for users who want free, low-bandwidth, cross-platform remote control of their systems. VNC runs on all Unix variants, Windows, and Mac.
But wait, you say, what about the X protocol itself? X is nice, it has been called a network protocol that draws pictures. However it is bandwidth-hungry, and works best on Unix machines. It's less helpful for getting to the majority of the applications running on your Windows or Mac machines."