|What causes different types of lightning? — CR, Tokyo, Japan
Cloud to ground lightning is caused by difference in electric charges between the cloud and the ground. Cloud to cloud lightning is caused by difference in electric charges among the clouds themselves. While I'm not at all expert on the subject, I would guess that the various different types of lightning discharges are caused by differences in the distances between charged objects, by variations in the local electric conductivity of the air and clouds during a discharge, and by the sizes and shapes of the clouds and ground.