Presence

Clarity

Clarity help improve definition by boosting contrast in the in mid-tone and highlights. Often without blowing out the bright points. It also maintains detail in the shadows and blacks.

Vibrance

Vibrance boosts colours that are muted while leaving highly saturated colours alone. In a lot of images you'll notice cooler colours (Blues and Greens) becoming more saturated while warmer colours are affected less. 

Saturation

Saturation applies to all colours equally. And will make the colours in you image pop.

It's a good idea to try using Vibrance before Saturation.