This is an another little feature added in Windows Phone 8.1 Update. Till now, you can share your internet connection on your Windows Phone only through WiFi. This update brings you the option to select the mode of internet sharing. You can choose between WiFi and Bluetooth to share your internet connection. This could come handy when some low-end devices didn’t have the option to connect to WiFi.
Other than that, do you have any real use cases of using Internet Sharing over Bluetooth instead of WiFi? Let us know in the comments.