I think it is a cactus or succulent, but I am not sure. As a result, looking up tips for caring for it has been difficult.
Sorry, the pictures are over 2 MB, so I posted them on imgur.
If this is the wrong way to go about asking such a question, then please inform me of how I may go about it better.
Thank you!
There are many similar plants commonly called "rat's tail cacti." Your is hard to identify exactly, partly because it looks so unhealthy!
Being enclosed in a glass jar with no water drainage holes is just about the worst place it could be. Put it in a proper plant pot, in some free draining compost. Give it as much light and direct sun as you can, and don't over water it.
It probably wants to grow into something like this, if you give it a chance. (Image from https://cellcode.us/quotes/rat-tail-succulent-plant.html)
