Friends are born of shared experiences. That's why it's so easy to make friends in university - you are all basically in the same boat. If you went right after high school, you're all the same age, in more or less the same financial and housing situation, and are taking courses which you can talk about. I've lost touch with virtually all of my university friends, just because we have much less in common, now.

Most of my current roster of friends are people that I work with, or used to work with.

I'm close friends with an ex-girlfriend.

I have a couple of friends I met socially, but don't see much of these days.

I have a few friends I chat with at my gym... but don't socialize with outside of the gym. Does that count?

(BTW... I dated 2 women from my gym... did NOT work out! So from here on, what happens at the gym stays at the gym.)