Noise rock bands can generaly be split into two groups:
The ones that just want to make noise (usualy pure white noise).
And the ones which think about the noise they make (music which uses avant garde "noisy" techniques to it's advantage).
The ones which just want to make noise tend to make noise which is 100% avant garde and does not use melody harmony, chord structures or any of the musical techniques which most people asociate with music. Instead they tend to overload their amplifiers as much as possible, to make feedback and scream over the top of it to make what most people would describe as pure white noise. An example of this kind of noise rock is the band Hijokaiden.
The ones which think about the noise they make tend to be more musical in their aproach, utilising techniques from heavy metal, punk, rock, math rock, post rock, kraut rock, phycedelia, computer game music and several other musical genres and combining them with the avant garde and noisy techniques of the former, to make a unique and intense music, which many have compared to Free Jazz. These bands include: Big black, Melt-Banana, The Boredoms, Merzbow, scratch acid, the jesus lizard, Lightening bolt and many more.
Noise rock is strongly linked to and inspired by other genres such as: No-wave, math rock, post rock, grindcore, Jazzcore and many more.
Noise rock and Noisecore are not clearly definable as different genres, rather just two ways of describing the same thing.
Japanese noise rock is sometimes refered to as Japanoise.