My study of Physics has been mostly all Bio Physics. Can you briefly explain Dark Matter to me?

Question

So long as its not Star Trek's Anti-Matter, being the opposite of matter, I think I'll be able to follow along.

Answer 1

http://en.wikipedia.org/wiki/Dark_matter

Answer 2

By studying the distribution and temperature of the hot gas we can measure how much it is being squeezed by the force of gravity from all the material in the cluster.

It turns out there is five times more material in clusters of galaxies than we would expect from the galaxies and hot gas we can see. Most of the stuff in clusters of galaxies is invisible and, since these are the largest structures in the Universe held together by gravity, scientists then conclude that most of the matter in the entire Universe is invisible.

This invisible stuff is called 'dark matter'. There is currently much ongoing research by scientists attempting to discover exactly what this dark matter is, how much there is, and what effect it may have on the future of the Universe as a whole.

Answer 3

Here is a simple answer.  Dark matter is matter that does not interact with any force, except gravity.  So you can't see it.  Thus the reason for the dark.  But it is not a black hole.  A black hole is black because photons cannot escape the event horizon.  Dark matter is dark because it does not emit or reflect photons.