Human sexuality is one of the most interesting topics in the universe to me... I've been studying it mostly informally (but some formal education) for most of my adult life. There is an amazing universe of orientations, desires, behaviors, and choices, and it's all fascinating.
And it scares the crap out of a lot of people. The thought of sexuality being anything other than one man, one woman is frightening to significant portions of the population. Which is unfortunate, since it results in so much hate in the world that is, essentially, a waste of everyone's time and energy.
Anyway, here's a great "overview of sexuality" clip I discovered today: