Grindcore comes from the tradition of taking music, and taking all the musical elements out of it

Simply put, Punk Rock's answer to Death Metal. You either love it or you hate it. Either way, fans of it won't give a fuck if you do or don't.

Like hardcore, but more-so.

totally bollocks music, more like noise

a musical genre made popular by music television and the consumer habits of brainless middle schoolers in girl pants with pocketfuls of someone else's money, grind-core requires little if any musical talent. most grindcore bands gain a following by dressing up silly and sitting around at coffee bars and headshops talking about how awesome their band is like they aren't in it (well, that's what i did anyway)

a fast form of hardcore, usually more chaotic and spaztic.

comes from punk and metal, as the origanl branches of genre.

some grind bands use the high pithced screams, followed by the gutterrolls(pig screams).

some modern day grind includes:
me and him call it us
destroyer destroyer
see you next tuesday
robinson
o' captain! my captain!
heavy heavy low low

grindcore usually doesn't have time signatures or often it doesn't use theory. but it is still very complicated in the notes and chords they do use.

grind bands usually consist of:
1 to 2 guitarist
1 bassist
1 to 2 singers
1 drummer.

a minimal grind band, that i have seen, consisted of:
a guitarist and a drummer.
both screaming.

A extreme genre of Metal, which normally include heavly palm muted guitars, blast beat, screaming vocals, and complicated bass lines.

These Bands include
Cannibal Corpse
Napalm Death
Brutal Truth
Nasum
Anal Cunt

Slayer is not Grindcore, Slayer is Thrash Metal