Its a feature they're working on to add to FGU that will automatically update extensions that the extension author has signed up to be part of Forge.
I'm not sure, but I think they're also setting up as an extension marketplace so that extension authors that want to sell their work don't have to aim at D&D 5E (since that's a requirement to be selling something on the DM's Guild website, the only place currently allowed to sell extensions).