I am familiar with how to install, connect to a portal, create, and edit a web app using the WAB.
What I want to know, and what my colleagues want to know, is how does it work?
The scripts and the startup is installed and then connected to the portal. Changes are made to the script and appear in the web app and vice-versa.
This program is installed and set up in a way that I've never seen before and I wanna know the details!
Are you asking about WAB Developer edition or an actual WAB deployed app on a web server?
I am using the Developer's edition.
As Rebecca explained WAB Dev uses NodeJS. NodeJS has a built in web server and read write access to the file system using JS. I am not sure what more detail you are looking for, I can go into more detail if required.
I think that is a rather broad question, and may be better suited as a discussion.