Raw vs. block device. I'm confused.

[jpayne%bbn-vax at sri-unix.UUCP]

From:  Jonathan Payne <jpayne at bbn-vax>

Could somebody out there explain (completely) the difference between a
raw device and a block device?  Don't just say that raw devices are
faster 'cos I already know that.  Why two types?  Why doesn't adb'ing
a raw device work? (At least not when I tried.)  I think a lot of people
know part of the answer to my question, but if somebody knows EVERYTHING
I would appreciate a response.
	Thanks,
		J