Traditional beacon interactions are a one-way conversation. The Bluetooth beacon broadcasts an identifier or other static data advertisement and a mobile device listens. Any communcation between the mobile and the local system must happen out of band, over a network connection such as cellular or WIFI.
Data Transfer allows dynamic advertisements to be triggered depending on custom business logic such as time of day or current promotions. The host device (POS, Digital Signage, Rasberry Pi) can determine what to broadcast and when. Not only can the advertisement data be controlled dynamically, but a mobile device can communicate back to the beacon (and its host device) enabling advanced use cases including: