If I turn off the mobile widget it saves a lot of battery on my EVO when I am in my office. I noticed I still get text messages and phone calls. What does the mobile shut down?
If you are connected via WiFi then data will be transferred over the WiFi radio and not the mobile network. If you so choose, you could turn the mobile data connection off while connected to WiFi.
Mobile is basically 3g.
Text/Calls come through, but no data.
Wifi is basically a faster 3g. So technically your data can come through then. Wifi auto shuts down 3g when it is being used.
Don't forget with mobile off and not connected to wifi, you will get texts, but any mms (text with a pic or sound) will not come through, those use the data connection, either wifi or 3g....