nothing, none of the buildings do anything except give you experience
NOT true...Some of the buildings do more than exp only. The barns are used to store items you don't need to show, like bales of hay. And the chicken coop is a building, and you can throw 20 chickens in there to save space, and to make it easier to collect from them all at once. Same with the dairy farm, which IS ALSO a building. So the moron who said the buildings are ONLY for experience is wrong, wrong, WRONG. Specifically the grain silo, yeah, that's for exp. But there are other buildings as I have mentioned.