alright, im not a guy who thinks in genres anyway, to me every artist is kinda a genre...but here we go:
classic industrial is the cabaret voltaire and throbbing gristle era from 1973 to 1981.
1973 cabaret voltaire was formed in sheffiled, england, 1976 throbbing gristle in london, throbbing gristle members founded the label industrial records which introduced the name industrial as a genre, 1977 they released their first album on industrial records.
cabaret voltaire and throbbing gristle played a dadaists-advantgarde inspired music, which means, songs are not structured, they are more soundscapes themselves, also the disturbing shows on stage were part of the whole message. you really need the right ears to understand it. most people will be just bored by 80% of those tracks. some are structured and very catchy though.
throbbing gristle broke up in 1981, psychic tv was founded in the same year by two former throbbing gristle members, the first album was released 1982.
skinny puppy was formed in 1982 in vancouver, they released their first EP (Remission) in 1984 and the first album (bites) in 1985, which is the beginning of the oldschool industrial era, which is sometimes reffered to as post industrial, but this expression is imo bullshit and not so popular actually.
the end of this era is 1996 released skinny puppy album the process.
then there is a break in production from 1996 to 2000 or maybe even 2004 something, next major realeases are the 2004 skinny puppy album the greater wrong of the right and the 2005 nine inch nails album with teeth which featured both such a dramatic change in sound that this has to be a new era, i.e. newschool industrial.
ok does that make sense? its the first time i wrote something like this..
its very short, i skipped alot, but it should give an overview, the frame of the whole thing, which is indeed those mentioned bands, and if you want to know more about the music, the only way is to listen to it anyway, no need to describe it further.