Affiliate Marketing Secrets

I ask because, although I do a lot of “activities” outside of school, they are not necessarily school-affiliated activities, or with clubs. Like, I like to play the bass guitar & sing, and paint & draw, and study a lot of subjects on my own time. And writing is absolutely my passion. BUT these aren’t school- or club-affiliated activities.
So, in order to list this stuff on a college application, do they have to be sponsored by the school in order to be extracurriculars?
Although I am in a few clubs at my school, I would like to express to colleges how I spend my time in activities that aren’t school-related.
So, what qualifies an extracurricular activity? Is it truly just extracurricular, in that, it’s something you do that is EXTRA, or does it have to be like a sport, or with a club, or with the school?