You probably didn't enroll in this class thinking that you'd be spending so much time reviewing principles of electricity & magnetism, learning about small ions, conductivity, Maxwell currents and that sort of thing. No you probably thought (hoped?) the class would be mostly about lightning. And much of the class will be, beginning with this lecture. We'll start with a fairly qualitative look at lightning phenomenology. We'll concentrate primarily on cloud-to-ground lightning.
Broadly speaking there are two types of lightning