The main difference here is in the topping.  Both sweet rolls are filled with a butter, brown sugar and cinnamon filling, but cinnamon rolls are generally topped with a cream cheese or vanilla icing glaze.  Sticky buns are traditionally topped with caramel and pecans or other nuts. Also, with cinnamon rolls, the topping is added after the rolls have been baked.  With sticky buns, the topping is added to the bottom of the baking dish, then the rolls are baked on top of that.  You invert the pan after baking to give them that glorious topping.