If you're a Millennial and you were lucky enough to have a car when you were young, that car probably had a tape deck. For the Generation Z folks reading this: a tape deck is like a radio that comes with the car only it has a place to put your actual physical music in the form of those retro cassette tape thingies you've seen in movies set before 1995.
Cassettes had a couple of advantages over CDs, and also over the MP3 file. They weren't fragile to quick the same degree as a CD and frankly they had a better variety and quality of sound than MP3 files. However, they were easily destroyed by the players that would munch them up and spit them out. They were also bulky and they had to be rewound in order to listen to them more than once. You needed a special deck to duplicate them. That's why they were displaced by the more easily stored CD, and they both were largely supplanted by the digital world.
However, cassettes had one lovely feature which was that you could make a mixtape for someone. It was a playlist, but it was much more personal, and it was a physical object which you could keep in the car. Hopefully it was the ideal reflection of your tastes, just like your car was - and if that's the case, then tell us about it, and we'll guess the car in which you played it!