It works without JavaScript because it can render everything server-side. If the user has JavaScript it uses websockets or Ajax to fetch updates from the server, but if it doesn't have those it can just reload the whole page like you would with a CGI application.

"Qt, but for web applications" would be a short and basically accurate descriptor. You slot together widgets in C++ and it works out how to lay them out and connect actions taken by the user to your event-handling code, which lives on the server.

The PDF thing is for rendering reports to PDF, instead of HTML. Not useful unless you're in a corporate sort of space, but when you want a PDF report you do want something like that. The DB thing is an ORM that makes basic CRUD operations on your database easier.