The stepped leader is a stream of weakly charged particles. It's not very bright because so little charge flows from the cloud. The stream moves downward out of the cloud in fits and starts, traveling about 150 feet before stopping, and quickly starting again. Since the atmosphere is a good insulator, this weak charge snakes its way downward, often branching, trying to find the path of least resistance toward oppositely-charged particles. When each branch of a stepped leader forking from the cloud meets a rising streamer, multiple return strokes are generated. Each return stroke travels from the ground to the cloud in less than a half second, so all the channels appear to light up at the same time as forked lightning.
Stroke appears within a cloud or is obscured by nearby clouds. Flashes of lightning can illuminate entire clouds, making them visible from miles away. With sheet lightning, the observer is near enough to hear the thunder. Those farther away might report "heat lightning."
Flashes too far away for observer to hear the thunder. Like sheet lightning, these flashes are created by lightning bolts, but are in thunderstorms more than 10 miles away. Trees, buildings and urban noise can cut this distance to less than five miles. It's called heat lightning because it is seen sky overhead is clear. Often, air molecules and dust particles in the atmosphere refract the light coming from distant lightning, making the bolts or flashes appear orange.
Extremely rare, nearly phantom, luminous spheres. Less than three feet wide, these glowing balls have been seen coming from some of the more violent thunderstorms, which contain lots of lightning. In nearly all reported cases, the observers saw another form of lightning flash before seeing ball lightning. Lasting from several seconds to several minutes, the spheres can simply vanish after traveling slowly toward the ground. Usually no damage is left behind by ball lightning, but at times they have traveled through windows and screens, leaving behind burn marks. Reports of ball lightning have come from passengers on planes as well as from people in their homes or on ships. Still, some scientists don't believe ball lightning exists.
Recently-discovered colored flashes of light high above thunderstorms. Playful names such as "red sprites," "blue jets," and "green elves" have been given to these distinctly different forms of lightning. They shoot up from the tops of thunderstorms about the same moment lightning discharges within the storm cloud. Occurring in the middle of the atmosphere, red sprites look like the stems of carrots, while blue jets are small streaks of light with flared ends like the horn of trumpet. Green elves are nearly-invisible, glowing, jellyfish-shaped amoebas that spread across the upper atmosphere.