Lightning starts as inactive charges in a rain cloud. When the strength of the charge overpowers the insulating properties of the atmosphere and at that point it STRIKES. Thunder is caused by the fast extension of the air encompassing the path of a lightning jolt. Sometimes you can't hear the thunder because of how far away it is.
Please correct any mistakes in my answer!! I'd be happy to fix it!! :)
Thunder is a direct result of lightning. However, it is possible that you might see lightning and not hear the thunder because it was too far away. Thunder is caused by lightning.
