GNOME Games is described as 'Games is a GNOME 3 application to browse your video games library and to easily pick and play a game from it. It aims to do for games what Music already does for your music library'. There are three alternatives to GNOME Games for a variety of platforms, including Windows, Windows Mobile, Windows Phone, Xbox and Android. The best alternative is Nostlan, which is both free and Open Source. Other great apps like GNOME Games are RetriX (Free, Open Source) and RetroX (Freemium).
A front-end or user interface (UI) is the presentation and interaction layer of an app or website. Most modern emulator apps have basic game list UIs that you can interact with using a mouse/keyboard but not a game controller.
RetriX is an emulator front end for UWP, on all the hardware platforms it supports: it serves the same purpose as RetroArch but is built from the ground up to integrate as well as possible with Windows.