TL;DR: It is a JAMStack-style static site, which we publish with the Middleman static site editor.

However, there's a lot more to it than that, and it's always actively evolving.

There's not currently a page which summarizes the architecture, but there are multiple pages and docs which are focused on processes around editing and maintaining the site. Here is a link which is a good starting point to see what's under the covers and how we use it: https://about.gitlab.com/handbook/git-page-update/#11-start-...

HTH! -- Chad