I did not buy WiPod and using the Data SIM in my mobile handset.
My plan was to see if things are OK then I will buy the WiPod later - in fact any better UN-LOCKED more versatile (Means which has more LTE Bands as well as 3G Bands) WiPod which I can use with any Network.
RNDIS is a Network protocol used over USB for USB Tethering.
Read this from wikipedia:
USB is a port which can be used for communication using different protocols for different works such as RNDIS is used for USB Tethering, Mass storage mode is used for connecting as Data Drive, USB Debugging for Firmware/Software installation or up-gradation, USB OTG (On-The-Go) to connect supporting devices such as pen Drive, Data Card, mouse etc, are few to name.
It is also used for Charging.