Q. What is "stereo" Bluetooth?  I know what Bluetooth technology is, but wondered if stereo Bluetooth was any different?

A. Stereo Bluetooth means that the phone can send stereo audio to a headset in addition to mono (regular) audio.  Non-stereo Bluetooth just sends one channel, so you can talk and listen to a caller's voice using a Bluetooth earpiece that only fits into one of your ears.  Stereo Bluetooth sends both left and right channels so you can listen to stereo music using Bluetooth headphones that fit over both of your ears.  You can also use Stereo Bluetooth headsets for talking and listening during calls, as well.  Not all Bluetooth phones support Stereo bluetooth - some (like iPhone) are mono only.

Bluetooth can also be used to move files from your phone to another device.  You can use Bluetooth to send photos, address book cards, and other data between phones or between a phone and a computer.  Whether or not a phone supports Stereo Bluetooth doesn't affect its other Bluetooth capabilities - there are different "profiles" for these different features.