Answer: The electrical discharge from clouds to building or a tree is called a lightning streak. Lightning is caused due to the imbalances between storm clouds and the ground, or within the clouds themselves. Most lightning occurs within the clouds. The colliding particles of rain or ice inside storm clouds further develop the imbalance between storm clouds and the ground, and often negatively charge the lower reaches of storm clouds. Ground objects such as the trees and the Earth itself become positively charged—creating an imbalance that nature seeks to remedy by passing current between the two charges.