The feature was uncovered by 9to5Google, and shows the ability to share files and links with nearby contacts and devices.
With Fast Share, it looks as though you'll be able to use to detect your friends and family's devices in the vicinity, and then send them the files directly. No internet connection required.
In operation, it appears to be a sort-of cross between the existing send and receive function with the Files app by Google, and the Nearby Bluetooth functionality baked into Android.
The former of those is primarily an app for managing files and storage on an Android phone.
While having that as its main purpose, it also has the option to quickly send and receive files via Bluetooth or Wi-Fi directly between devices nearby. The other user does need to have the app installed as well in order to do this.
With Fast Share, one would presume that - since it's baked into Android - you'll no longer need to download another app.
The Nearby Bluetooth feature has been around for a couple of years now, and has been the easiest way to set up Bluetooth headphones or Google Cast devices.
Automatically, a pop-up appears on the phone's drop-down shade, showing that it has detected a pair of Bluetooth earphones ready to connect to. It was first shown off with the Pixel Buds.
By combining these two features, Google is creating an Android version of Apple's AirDrop, which lets you send files and information between nearby devices. It works across iPhones, iPads and Mac.
Like AirDrop you'll also be able to select who can discover you, by adding friends and family to a preferred list.
So far, it's not a default enable feature in Android Q, but it appears as though Google is at least testing it, perhaps ready for when Android Q is officially released later this year, or when the next generation of Pixels arrives.