3G data technology means you can access the internet on your phone at faster speeds than the normal EDGE network. Wi-Fi calling is very similar to a Voice over IP calling system such as SKYPE. However, for a phone that has the ability to do Wi-Fi calling on T-Mobile, you are able to use a T-Mobile Hotspot to make calls using Wi-Fi as opposed to your normal minutes. Lastly, Windows Mobile 6.1 is just the operating system for your phone. Similar to your computers operating system, it is a smaller scale operating system set to work on your mobile device.
-Michael Cera
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