The General Theory of Relativity, Quantum Mechanics, Black Holes, Stephen Hawking, String Theory, Hawking Radiation, Singularities and the Theory of Everything.
I had to promote this episode from NGC’s Naked Science series as it helped me understand a bit more about these concepts and their inter-relation in the short span of 60 minutes. Something that my physics teacher failed to do in 6 years of classes :).
Fascinating stuff, catch the full episode if the topics interest you.