Switching Between 3G and Wi-fi -- How Does The Phone Know??

[Reinkster]

I have a Samsung Jack w/ Windows Mobile 6.5.  In the Settings \ Connections \ [Right Click] Advanced tab I have multiple options for the 4 different connections:

Internet connection: MEdia Net [default]

Work connection: Automatic [default]

WAP connection: MEdia Net [default]

Secure WAP connection: Automatic [default]

First off, I have no idea what AT&T means by these connections; I'm fairly computer saavy and this isn't very clear.

My issue: When I have a Wifi signal, I'd like the phone to use it instead of the 3G data network.  Unfortunately, I can't find how do clearly set the phone to do this.

When I changed Internet connection to "Automatic" and was connected to Wifi it was BLAZING fast.  However, when I lost the Wifi signal, the phone did not automatically switch back to 3G data.  It was stuck, dead, "no data connection".

All that said, anyone have some advice on this?  Currently I am using the 3G signal for all phone activities, since the wifi is basically useless unless I constantly switch the phone settings.

Thanks,

~Adam