Highlighting products are great makeup tools to use to bring light to your face. By bringing light to your face, you are drawing attention to your face or areas of your face. It is the opposite of contouring, actually. Highlighters bring out your features with a touch of light, luminosity and radiance. When done right, your face will glow, like lit from within and no one will know why.
Highlighters are tricky. You don't want them to be too shimmery, yet you don't want them to be too flat and not show up at all. I have tried many of them (of course) and have six highlighters that I depend on.