What is cloud to ground lightning and how is it formed?
Lightning is basically a discharge of energy, or electricty within a thunderstorm. Lightning forms when two different charges build up within a cloud, between clouds, or between the cloud and the ground. A good example is a battery with different charges on both ends of the battery -- positive and negative.
Cloud to ground lightning begins when negative charges begin to build at the base of a cloud. This creates something we call a stepped leader. This is the initial discharge of electrons or negative charges from the base of the cloud to the ground. The stepped leader is very faint (it can barely be seen) and it does not reach all the way to the ground.
The stepped leader causes positive charges to build near the ground, on trees, and on buildings. This creates what we call a return stroke which begins from the ground and moves upward toward the cloud to meet the stepped leader. The return stroke happens so quickly, we just see it as one continuous lightning strike from the cloud to the ground.
Other types of lightning occur from different charges that build up within a cloud, such as cloud to cloud lightning.
Here are some websites you can visit to read more about lightning: