The Stove Theory:

A typical stove (and by typical, I mean "every one I've worked with) has four burners. As a right-handed person, I use the front right burner the most often - on the (admittedly) rare occasions when I cook. The next most used is the front left, then the back right and finally, the back left. To begin a metaphor, the people in your life can be divided into four regions: the front right burner, front left burner, back right burner, back left burner.

FRONT RIGHT BURNER: These are the people you think of first when you get good or bad news. If you won the lottery, this is the group of people you would call first. This would probably include immediate family, significant others, and ridiculously close friends.

FRONT LEFT BURNER: These people are friends, just maybe not as close as the front right burner folks. If you won the lottery, you would probably call them to tell them to watch the press conference on the news.

BACK RIGHT BURNER: These people are acquaintances-going-on-friends. Maybe you email them every once in a while, but there's no consistent two-way communication. You still need to pay attention to them, but...yeah. If you won the lottery, you would probably send a quick "thanks" email when the congratulated you.

BACK LEFT BURNER: These are people you know but not that well. Perhaps friends of friends. If you are left alone with this person, you will have an awkward conversation, but you certainly don't seek them out.

The metaphor continues with various places in the kitchen (I once described my relationship with a girl as "I'm not even on her stove. I'm in the pantry...of her RV...that's going off a cliff...on Mars."), and really, the only limit is your imagination.