What is GOG?
GOG.com is basically a video game platform like Steam and Itch.io but with an emphasis on all of its games being DRM-free and initially old video games that have been ported to work on modern systems. Now it also includes modern video games as well as the old ones. I've been getting most of my video games from there because of how you can download offline installers for the video games you buy from them and that you don't have to use a launcher to play your games.