The super-heated air expands outward explosively, producing the shock wave we hear as thunder. The bright flash of glowing air is called the return stroke since it moves from ground to cloud, opposite to the moving charges. The return stroke discharges a region of the cloud, but the cloud can reorganize quickly and as many as 40 strokes have been observed to use the same charged channel. There is quite a lot of energy in a lightning stroke, about 250 kilowatt-hours. Lightning doesn't always travel from cloud to ground.
Lightning can also arc from one cloud to another.
The typical type of lightning is called streak lightning, or forked lightning. If the lightning channel is blown by the wind during a multiple discharge, each succeeding stroke is displaced by a short distance, making it appear as ribbon lightning. On rare occasions the lightning seems to break up into beads that persist for as long as one second, an unexplained form called bead or chain lightning. Sometimes the lightning flash is obscured by clouds, which are then brightly illuminated. During this sheet lightning, the flash seems to come from everywhere.