(1) At the outer rim there are “casual friends,” those people who you are always happy to see and they are happy to see you, but there is no investment beyond that.
(2) There are “buddies” who are the ones who just want to hang out/have fun. They’re the ones who come to your parties, go with you to movies, and want to know if you’re hosting a game or something else fun. Do not call these people when you move or need anything, they WILL disappoint you. You’ll notice that when they ask you for a favor it feels like an imposition.
(3) There are “good friends.” Sometimes not as fun as buddies but they are really, really good people and there is a mutually supportive energy that binds you. These are the people who can call you at odd hours to ask for a favor and you will happily do it. On some level you know that the favor/karma will be returned.
(4) Last but not least are “true friends,” the inner circle, the sanctum sanctorum. These are the people you marry or adopt in that “friends are family you can choose for yourself” sort of way. Sometimes they are harder to get along with than good friends because the investment is so deep and you expect/hope for so much from them. These are the relationships that make you say things like a bad day together is better than a good day apart. Sometimes you’re downright inseparable.

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It’s actually scary how accurate that is. Sadly I’m currently lacking 3 and 4.