Aristotle figured there were three kinds of friendships:
1) Friendships of utility: exist between you and someone who is useful to you in some way. For instance, perhaps you’re friendly with your cubicle mate mainly because she helps you figure out the printer when it jams and–if you’re an IT guy–you pretend to fix her computer in some top-secret-awesome way when it freezes, although all you really do is re-boot it. Or maybe the two of you take turns going out on coffee runs. Possibly you’re friendly with your neighbor because she waters your lonely little cactus when you got on vacation and you take care of her Great Dane when she’s away.
These are friendships of the “You scratch my back, I’ll degrade myself by picking up your pooch’s poop with a plastic baggie” kind.
2) Friendships of pleasure: exist between you and those whose company you enjoy. Often, these are “activity buddies”: people with whom you do things like playing soccer, going for long bike rides or cow-tipping. You may have this kind of relationship with one of the other locals at your friendly neighbor coffee shop or gym or tattoo parlor–the kind of person with whom you enjoy a little chit-chat or a good joke.
(Would “friendships with benefits” fall into this category–because you’re both enjoying the sexual pleasure? Or into the first category, because you’re using each other for sex? Good question. But I think casual sex is a bit closer to #2, because The Big A. says friendships of pleasure come about because we do like some–or many–aspects of the friend. We might like his wit, her compassion or his flirty manner, for instance. Friendships of utility, on the other hand, exist mainly because the person can help us out in some way.)
3) Friendships of the good: are based on mutual respect and admiration. These friendships take longer to build than the other two kinds–but they’re also more powerful and enduring. They often arises when two people recognize that they have similar values and goals; that they have similar visions for how the world (or at least their lives) should be. Not infrequently, they begin in childhood, adolescence or college–though plenty form after that, too.