getting into the math of poker

[TheWorm967]

I read a post the other day about the levels a poker player goes through, and it mentioned that you've reached a certain level when you start to get to the math of poker. I've also seen some of the better players do up seemingly complex equations when disussing a hand, like bayes therom which made me cry.

My question is how can i learn this math? Is it as difficult as it looks? what resources are there to help with this sort of thing? and lastly is it essential to becoming a great player?