Not heard of Norwegian Black Metal before. There a Finnish metal group I listen to. Nightwish. Betting not close to the same thing.
Oh boy, the lore behind this genre lol
I don't generally listen to this type of music, but I know all about it. It's fascinating.
A decent place to start is maybe with Burzum, Emporer, Mayhem....learn about "Euronymous", "Dead", and Varg Vikernes, and what unfolded there....Suicides, stabbings, church burnings, etc...
Main difference between black metal and other extreme metal is subject matter, generally anti-christian themes alongside ethnic paganism (old Norse mythology is quite interesting, shares some parallels with ancient Greek and Roman mythologies, but is also unique to itself)
Old school black metal was distinguished by poor sound quality, virtually non-existent production, extreme speeds, and usually a higher pitch shrieking style vocals as opposed to the deeper gutturals more typical of death metal.
As with everything metal, it isn't so cut and dry anymore...there's an amalgamation of styles and themes.
I think there might be a documentary on Prime or somewhere that covers all this pretty well. I'd bet there's a few of them actually.