"Shimano is launching an electronic shifting system for high-end road bikes":

By replacing the conventional levers that pull wound-steel cables through protective housings with solid-state switches and rubber-coated wires, there's no chance for road gunk to clog things up and interfere with shifting, or, for that matter, your post-ride beer...

The derailleurs, whose job is to move the chain from gear to gear as you shift, talk to each other and automatically adjust so the chain doesn't rub. They also calibrate themselves, so you don't have to play with cable tension to maintain shift quality as cables stretch and the chain and cogs wear.