What is lightning?
How lightning works (into more detail) (electrostatics)
-A streamer of electrons then is attracted to the ground because the surface of the ground is positively charged.
-As the streamer of electrons approches the ground, the positive streamer is repeled by the ground and is attracted by the negative streamer.
-When the streamers connect they have a fairly good conductibility allowing electrons to jump to the ground, this is lightning.
see video below.
Fun lightning facts
The physics classroom, Electric fields: Lightning,
Flash facts about lightning: National geographic
How stuff works, How lightning works,
Science joy wagon, Lightning physics