If the question doesn't make sense, I'm basically asking how can I play a game by streaming it(?) off of another computer?
I wanna play on higher graphics, but it seems I likely cannot upgrade my current graphics card (maybe I can buy another one and insert it? I dunno, and that's not the point)
I've heard of apps that you can use to start a game and play it off of some other PC. How do I do this? Is it cheap? What program do I need?
Even though you posted this in the Planet Zoo section, I'm going to answer it as a general question.
I have an aging PC. It's at least 6 years old, although I did recently upgrade the motherboard. You can see my specs in my sig.
I play sometimes on NVidia's GeForce Now, a cloud streaming service. I can play for free but I get a 1-hour session, with unlimited sessions. As my 1 hour is drawing near, a timer appears and at the 1 hour mark I am logged out. I can re-log back in straight away, but there might be a queue depending on how popular the game I want to play is. If I pay a monthly subscription, I can play for a 6 hour session (I think they are bringing in a higher tier than that).
This requires me downloading and install the GeForce Now program on my PC. Once I've logged in and connected my Steam, Epic, Origin or GOG accounts, any game I own on those accounts, that GFN supports, I can play. Here's a list of games that is updated every Thursday
https://www.nvidia.com/en-gb/geforce-now/games/
Any cloud gaming service works similar to GFN. You sign in on their app, program or site (I found the Microsoft Store via XBox Game Pass for PC does cloud gaming) and can play games they support. Google tried it with Stadia, but it didn't take off, probably because unlike GFN, even if you already owned the game, you had to buy it again on Google's Stadia AND pay a subscription fee.
You will need a stable internet connection. I manage just fine on about 100Mb/s download. With GFN there's almost no latency (if there is any, I haven't noticed it), I don't have any experience of any other cloud gaming service.
I hope this helps.