Windows Phone 8 uses Hubs and application sandboxes to store and access user files. You can browse and access the files that are stored on the phone by accessing the hub or app that is used to view and work with the file. Files that are stored on a phone must be associated with a Windows Phone app (native or third party) and files are stored in the associated [opening] app’s hub or “sand box.”
Windows Phone 8 can receive and store files that are shared with it from another Bluetooth connected device. Bluetooth shared files are stored in one of the hubs on the phone or in a compatible app’s sandbox.
Receiving Shared Files via Bluetooth
When a Bluetooth-enabled device shares a file with your Windows Phone, you’ll be prompted to “accept” or “ignore” it (in this example, my laptop which is named AVALON48 is sharing a file with my Nokia Lumia 920).