It is just a bracelet. They used to hand these out when I was a kid. https://i.imgur.com/Nm8NWEm.jpeg

It's a friendship bracelet. Back in the late 80s and early 90s friendship bracelets were super popular in elementary and middle schools. The idea was that you and your friends would make them by hand and give them to each other. I'm sure they're probably low key still a thing, but their popularity at the time was pretty much on par with how popular fidget spinners were a few years ago, so you could buy mass-produced ones in all the same places you could buy fidget spinners: gas stations, grocery stores, etc. This was the most common style of mass-produced one.

Looks like a pretty shitty prusik loop. Usually used in climbing or other ropes applications. A good prusik would be of a better rope quality and the knots would be more robust but same principle. More likely a summer camp bracelet of some kind.