When lightning strikes within one cloud it is called

Intracloud lightning is when the lightning strikes are within one cloud. This is actually the most common type of lightning in the world. The lightning is within one single storm cloud. it is also called sheet lightning because of the way it lights up the sky. It can all be obscured from the cloud or only partly obscured. Many times it is confused with ground to ground lightning.

The answer is intracloud lightning. Lightning can occur between clouds and ground, which may be downward (the lightning is originated in the cloud and goes to the ground) or upward (the lightning originates in the ground and goes to the cloud). As the question tells the lightning can occur inside a cloud, that is why they are called intraclouding lightning (intra means inside). Also lightning can occur between clouds and air.