I haven't used GAE, but if I generalize your question a little bit then I can answer it in the context of Django. You run a WSGI server that receives HTTP requ

I haven't used GAE, but if I generalize your question a little bit then I can answer it in the context of Django. You run a WSGI server that receives HTTP requests. It uses the regex-based URL mapping you write in your Django app to work out which view function to call (and, optionally, with which parameters). This function talks to the database, runs whatever logic you need, collects the relevant data for the UI and uses it to render a template, the result of which is then returned to the user. Django templates look a lot like HTML, but with special Django stuff in them. You can get the general idea from this page: http://docs.djangoproject.com/en/dev/ref/templates/builtins/ http://docs.djangoproject.com/en/dev/ref/templates/builtins/ And yes, you write in JS pretty much the same stuff that you'd always write in JS.