What exactly is it, what is the differences between say deathcore and slam death, what are the main differences, does it have more than one sound? All the slam i have heard sounds like devourment.
It's basically a slower "brutal death metal" with emphasis on slamdowns and breakdowns. That's probably all it really is, so you can do a lot with it and it can still be called "slam death" if you just follow the basics, combine it, or whatever.
Most brutal genre of metal to ever exist besides grindcore/goregrind. And yes, with slams and breakdowns. Think an improved version of deathcore and 1000 times more brutal.
Bands like Guttural Slug, Visceral Disgorge, Abominable Putridity, Vulvodynia, Kraanium, Cerebral Bore, Cerebral Incubation, and Short Bus Pileup.