Acquaintances, Friends, Fair-Weather-Friends, Good-Friends, Best-Friends, Life-Long-Friends. There are lots of categories of “friends” because there are lots of reasons or circumstances why people jump to another category of friendship or stop being friends.
For me there are only two categories, “friends” (the life-long type) or “acquaintances” (everyone else). I don’t put a lot of stock in the “everyone else” category. I don’t expect they will call me to “hang out” or remember my birthday or even be around next year. On the other hand I expect them to feel the same way about me. However if they do show up at the house I will feed them, buy them a drink at the bar, or chat occasionally with them. But I don’t expect they will be there begging to help me move (a true sign of a Life-Long-Friend) or have me as a necessary part of their life. In keeping with this point of view on friendship, people don’t disappoint me. If one of my "acquaintances" gets a boyfriend or girlfriend they may drop off the face of the planet and I won’t hear from them until they break up or get thrown out of the house. Life-Long-Friends don’t abandon you because they have someone more interesting or who is jealous of their time or who puts out.
Life-Long-Friends help you and care about you no matter what or for how long. They keep in touch. They find out when you need help and they offer to help or just plain show up. They are involved with your life. I am talking a two way street here. You do the same for them.