Thunderbolt carries video, FireWire and USB. Apple's party line is that Thunderbolt displays require Thunderbolt computers - but they also say that Thunderbolt is pin-compatible with mini-DisplayPort, so you can use the Thunderbolt port on 2011/2012 computers with the mini-DisplayPort connector on pre-2011 monitors. I've been wondering about this ever since Thunderbolt was released.
