Can adjust tones separately - shadows, midtones and highlights.
Preserve Luminosity button. Normally keep this checked. If this is not checked, then it gives the same effect as a Curves Adjustment. Checking it is more useful and even though it can be done with curves it becomes very complicated very quickly with multiple adjustments. (Ref).
The 3 sliders are similar to the 2 sliders in Photoshop and Lightroom for adjusting colour temperature, but far more useful.
Can use split toning to apply different colour tones to the shadows and highlights.