Can someone please explain me what exactly LoopBack is?

Hi,

In my recent project the client requirement consists of this word LoopBack and so I started learning about it but still cant find what exactly it is. Through my learning I found it is built on ExpressJS and creating modules and also we can create and use client memory and also can include various DB's.

I hear that it bridges the gap between server and client but the question is where is my server.js code? When I'm changing the data's it's reflecting in my DB so is it acting like a GUI?

Please correct me if I'm wrong since I'm completely new to LoopBack.