Oils

While cruising the Internet, I found this post on Eating Rules about cooking oils.

We are pretty much an olive oil or vegetable oil family. I'd like to branch out to some other oils, but I've never known what to get or what it's good for. And truth be told, we've had the same bottle of vegetable oil for about 8 months.

I use 2 Tb of oil in pancakes. I can't think of anything else I use oil for. Muffins occasionally. And hummus--that's what the olive oil is for.

I guess what I'd really like to know is the difference between butter, oil, shortening. Then there's lard. I know nothing of these and just use butter most of the time.