It will advance to the next frequency in the normal steps for that band when you are holding on a channel. If you push it in, it go to the next programmed channel. Pushing it in changes it's function back to frequency, etc. VFO is a term that relates back to the days of a manual tuning dial on your radio or Variable Frequency Oscillator on your short wave set, so in this case, it tunes to the next frequency in steps.