Vercel resells servers with additional stuff ontop. When you commit code to a git repository, vercel (optionally) runs a build step (like you would on a workstation). It takes the resulting files (HTML, CSS, JS, ect), and sends them to many servers around the world. When a user requests your site, it chooses the closest one. Those servers are also capable of running small scripts when information is requested from them, to add dynamic content. Metaframeworks (some combination of a backend (like Django) and frontend (like React) framework) can generate this dynamic code.
--- End explanation, que personal thoughts) ---
I quite like this "serverless" methodology, for a variety of reasons. While it's a paradigm shift, it makes my life so much easier. For simple sites, I just write my static files, commit them, and spend... I suppose less than 30 seconds clicking buttons. I never need to worry about server maintenance, uptime, or security. I never need to think about updating remote files. It's also incredibly cheap for my hobby projects, as I'm not renting a server that duplicates the work of every other one on the rack.
What ever happened to just S/FTP your files to the web server.