CANBUS is an acronym for Controller Area Network Bus, originally developed by Bosch... the same company that also developed the first O2 sensors, BTW...
CANBUS enables the manufacturer to greatly simplify the wiring harnesses for electronic components, which can reduce costs and improve the reliability of the system. They don't have to run individual wires to carry discrete signals from each switch to the component to be controlled. CANBUS is a message-based system, which we've been using in computer systems for decades. Harley is finally catching up to this system. It eliminates most of the point-to-point wiring because everything goes over a high-speed data bus. Messages are sent from, say, a switch component, to a cruise control component, telling it to do something... instead of a signal being sent over a dedicated wire between the switch and the controlled device.
CANBUS vehicles have a LOT less wiring than older point-to-point discrete vehicles like pre-2011 Softails, and pre-2014 Touring bikes.
Think of it as a kind of Local Area Network on your bike... on which all of the components and switches "talk" over common wiring.
Reference:
http://en.wikipedia.org/wiki/CAN_busKen