It's called LaTex. I'm just becoming familiar with it myself. I found some pdf's online (simple google search) that serve as a useful reference.
To get started, you might do what I did - click "reply with quote" (you can cancel if you don't actually want to reply) to see how others get write it.
I also think there might also be some forums here, in MHF, that discuss it. If so, I can't speak to their value - I haven't looked at them (I still don't know my way around here all that well.)