Lightning is a giant spark of electricity in the atmosphere between clouds, the air or the ground. In the early stages of development, air acts as an insulator between the positive and negative charges. When the opposite charges build up enough, this insulating capacity of the air breaks down and there is a rapid discharge of electricity that we know as lightning.
The incidence of individual lightning strikes in any particular place is highly variable, but lightning does have a spatial distribution. Previously, the frequency of lightning over the surface of the Earth was estimated to be 100 times a second. But, in 1997 NASA and NASDA of Japan launched the first "Lightning Imaging Sensor" equipped satellite to detect and record lightning.
Lightning is now known to occur on average 44 (± 5) times a second over the entire Earth, making a total of about 1.4 billion flashes per year.