Lightning originates in the sky, but the part of the cloud-to-ground lightning visible to the human eye comes from the positive electrical charge that responds to the invisible negative electrical charge sent from the clouds. Lightning helps the ground and the atmosphere exchange and balance positive and negative energy.
Lightning is caused by electrical charges in the atmosphere. As opposite charges build up, they break through the insulation provided by the air and send an electrical burst within the cloud, to the ground or to another cloud. The lightning can come as either a positive or negative charge. Positively charged lightning is more dangerous to people than negatively charged lightning.