Ya, I still don't understand how this works at a high level. Does anyone actually understand how it works?

A Gemini client is an application like a web browser, but simpler. It sends a one-line plain text request to a Gemini server over a TLS socket. The server sends back a document with a MIME type, or an error message, and closes the connection. The client renders the response for the user. That's basically it. It's similar to Gopher or to HTTP/0.9. A common document type returned is Gemtext, which is a text format like a simplified Markdown that can be parsed on a line-by-line basis.

Given the amount of servers and clients people have written for it[0] I'd say there are definitely people out there who understand how it works. What don't you get exactly?

0: https://github.com/kr1sp1n/awesome-gemini