I dabbled in a bit of neography (creating your own writing system) and a hint of conlanging (creating your own language). I think I've managed to create a fairly decent writing system for myself, but the conlang went nowhere fast as I underestimated the effort required to even get started with it. I also attempted making fantasy maps, but it was all in paper and quite a while ago.
That's it, I suppose: neography, conlanging, and fantasy mapping.
I also spent an embarrassing amount of time looking at maps and making virtual road trips via Google street view, but that's way more mainstream.
That's cool. I would try to get into get into conlangs, but I don't feel strong enough with my linguistic background to try now. The farthest I ever got was creating alternate alpha-characters ages ago in class with a friend.
I have always liked maps and then I found the mapmaking and worldbuilding subreddits a while ago and have always wanted to do that, but I get overwhelmed and unsure where to start. Its one of those ideas I can't shake though so I will probably give it a good shot at some point in my life.
Lack of knowledge in linguistics (or languages in general) is also what stopped my conlang project in its tracks.
As for creating alternate alpha-characters, that's where I got my start. I thought it'd be cool to replace Latin alphabet characters with my own symbols, and things went on from there. Like, I think it's nifty to have a symbol for the 'sh' sound, or I've noticed that I encounter a certain sound combination a lot of times. And then it got kinda out of hand and I decided to simplify things a bit, and then added back more symbols, but with more thought given to it this time around. A few more cycles of that happened over the many years I've worked on my script.
In this context, as in the more ordinary sense, it is a mapping of speech sounds to symbols, usually written, but some others have made systems that make use other things such as color (lights, or pigments) or even 3d-shapes. So, for example, the Latin alphabet is a writing system, but so are the Arabic abjad, the Devanagari abugida, the Mongolian script, the Korean script, Gregg shorthand, as well as Tengwar and Klingon. The last two are considered conscripts (a synonym for neography, in hindsight, I should have used that instead) since they aren't used to write "natural (human) languages".