It's got these great visual aids of SIMS like people in all the sex positions that one could possibly dream of. It's mostly male/female, though some of these could obviously be used for other gender combos. How many of these have you tried? Some of them look downright IMPOSSIBLE. Some look like you would have to be a contortionist or have super strength to keep up, look at this one: link
How is that possible? He looks like he's trying to poop on her.
Or this one: link
Another "I'm trying to take a poo on her" position. Who has a penis that twists that way?
Anyway, I thought it was a handy list to keep for reference.