It's basically a web frontend to allow you to manage, organize, and download roms that also has the ability to play roms for certain systems in the browser using Emulator.js. The idea is with this you have a self hosted repository of roms with nice box art and meta data that you can download to any device or optionally play in the cloud if you want as well. I installed it a few days ago and it's really slick! It didn't handle the metadata for every game perfect, but for what it is it shows a lot of promise.