All your files which would normally have to be uploaded to several workshop addons or to your fastdl get compiled into one GMA. This gma is downloaded and uncompressed by each client, once ingame, thus allowing you to serve your clients your files easier, quicker & when they're fully loaded instead of causing them to be stuck at the loading screen. The second thing it does is changing the way workshop addons are loaded. Instead of downloading workshop downloads while at the loading screen it moves them all to when they're fully loaded. Those 2 factors combined reduce your loading times greatly