Load an audio file, set the shift in semitones between -12 and +12, and press Apply. Preview the shifted result in the player and download it as a WAV when it sounds right.
The tool first time-stretches the audio by the pitch ratio and then resamples it back by the same ratio. The two operations cancel out in duration but not in frequency, which leaves the pitch shifted and the length untouched.
Two or three semitones in either direction is usually transparent. Beyond about six semitones the granular stretching becomes audible as a slight warble, especially on sustained tones, so use large shifts deliberately as an effect.
Yes, that is one of the most common uses — shift a backing track down two semitones to suit your vocal range and the tempo stays exactly the same, so you can still play along with the original timing.