Marek uses this abilitiy while traveling and while weilding Blackout. It simply bends light around him to make it seem as if he is invisible. This is to help give the illusion that he is not in fact there. It all complements his strategy when using Blackout.
When Rock Lee uses this technique, he runs at a fast pace, fast enough to create multiple afterimages of himself. Tenten calls this a mirage.