What is dark matter in relation to black holes ?

Answer 1

Dark matter is a substance that does not compose every day visible objects (including stars) but should be there because galaxies behave as if they weight significantly more than the observable mass (that of the stars and gas clouds).
Black holes, on the other hand, and despite their rather extreme physical characteristics are indirectly observable as they do interact with other objects, the mass that falls in a black hole is emitting huge amount of radiations as it gets compressed and accelerated in the accretion disk, also black holes are formed by the catastrophic collapse of ordinary matter objects, namely the core of stars that went super nova. Dark matter, as far as anyone can tell, does not appear to be clumped in objects.
All this is still highly conjectural, as no direct observation was made of dark matter, and thus subject to revision if and when more is found about that elusive stuff.

Answer 2

Black holes where thought to be dark matter, like when they were searching for the missing mass of the galaxies. But they calculated that black holes did not make up a significant amount to be dark matter.

Read 'The Omega Point', its a book about dark matter.

Answer 3

The are both forms of matter that cannot be seen directly, but by via their gravitaional effect on other things. Other than that, there's no relation. Primordial black holes of low mass were once a candidate for dark matter, though, but were ruled out by the lack of observable Hawking radiation.

Answer 4

They're not connected by any theory I have ever heard of.