An avocado is a bright green fruit with a large pit and dark leathery skin. They're also known as alligator pears or butter fruit. Avocados are a favorite of the produce section. They're the go-to ingredient for guacamole dips. And they're turning up in everything from salads and wraps to smoothies and even brownies. So what, exactly, makes this pear-shaped berry (yes, that is right!) such a superfood?