It's a service where you put in the web address that has the pictures you want to check. It runs a search of the web and checks to see if it can find the picture anywhere else. It's not a guarantee that the picture is "real" if there's no hits...keep that in mind.
But if that 20-something hottie posting on eros or backpage looks amazing and will rock your world for 150 an hour.....and her pictures are found on teen-porn-my.ex.girlfriend-euro.hotties-Czechoslovakia.com..............she's prooooobably not real.

Just sayin'