What is lightning?
Lighting is the atmospheric discharge of electricity. This electricity is the result of static charges that build up after being generated for reasons that are not clearly understood. Note that any simple action resulting in friction, like pulling plastic wrap off a roll or shuffling across a rug on a dry day, will generate static charges. Moving air can separate charges, and ice is thought to be involved, but the mechanism is not completely explained by science.
When charges are separated, an electrical force appears between them. This force is voltage, the electromotive force. As more charges separate, voltage builds, and at some point, this voltage will be so great that it will ionize air between the charges. Current will flow along this ionized path, and this is lightning. Moving electrons carry the current. The ionized air is superheated, and it emits an intense light. The light we see is the lightning, and the superheating of the air creates a shock wave we perceive as thunder. The bolt can pass from ground to cloud, from cloud to ground, or from cloud to cloud. Links can be found below for more information.
Lightning is a natural phenomenon of electrostatic discharge breakdown that occurs when static electricity builds up between thunderclouds or between the cloud and the earth.
If the difference in electrical potential between two points is more than 100 million volts,
it produces a plasma during discharge, causing an explosive expansion of air by heat. By dissipating, this plasma creates a flash of light and thunder.