Most of the lightning people see takes place between a cloud and the ground. But lightning also occurs within a cloud, between a cloud and the air, and between two clouds. When Lightning occurs in the atmosphere, its electrical energy scatters in the air. This energy may damage airplanes but it does not cause harm on the ground. But lightning that strikes the earth may kill people or cause fire.
Lightning is caused by the movement of positive and negative electrical charges towards one another.
During a storm, a thundercloud's particles collide and become electrically charged. This results from the unequal sizes of the water droplets in the clouds. When water falls through a rising column of air, the larger spaced-out drop break up into smaller drops The larger of these drops, higher up, possess a positive electrical charge. The smaller denser falling drops have negative charges. When the buildup of electrical energy between the large higher positive droplets and smaller negative charged areas in the cloud reaches a peak, we have inner-cloud lightning.