[James]

I am really stumped, I would like to know how it is possible for Dark matter to exist?  What exactly is it and what types of dark matter are there?

[Tetrahedrite]

If anyone on this forum could answer that question accurately they would probably be rich and famous!!!
However I will give it a shot.
Dark matter is believe to make up 90% of all matter in the universe. I believe the current theory is that particles called WIMPS (Weakly-Interactive Massive ParticleS) are responsible for the dark matter. The problem is, as their name suggests, these particles do not interact with light or other matter and thus cannot be seen and are extremely hard to detect by other means. Physicist believe this matter has to exist because mathematical calculations show that the rate of spin of galaxies cannot be explained with the visible matter in those galaxies. Unfortunately that's about as much as I know, hope it was some help

[TigerFX]

Wikipedai has a good article on dark matter.