What is the difference between FM radio and Stereo FM Radio for a phone?

A phone with FM reception tunes into the same signal that a home, car, or portable FM radio does – and whether it’s Stereo or Mono depends on the station transmitting the signal (though if the stereo signal is weak, then the radio will probably switch to mono automatically as it will improve reception).

The good reason for having it on a phone is that it does not use any internet data – so does not affect your download usage.

If you’re going to use it regularly, it’s best to be in an area with a strong signal, as the antenna is often not very good – they often rely on using part of the headphone cable.