A juxtaposition occurs when you place side-by-side two objects that wouldn’t normally be seen together. Doing so emphasises the properties of each object by contrasting it with the other. Imagine that you’re at a fashion show, watching (allegedly) glamorous models striding down the catwalk: after seeing the fiftieth fancy outfit they all start to blur together and none stands out. Suddenly, a car mechanic dressed in oily overalls appears in the middle of the line of models and strolls along with them. Now you are acutely aware of the fancy femininity of the models’ outfits because when they are juxtaposed with plain, dirty overalls your senses are awakened. Moreover, you notice the overalls far more than you do when you walk into a garage, and you’re likely to think about the differences between the lifestyles of models and mechanics. The juxtaposition has made you much more aware of the nature of models and the nature of mechanics, and done so on more than one level. If you made a photo that showed the mechanic among the models the juxtaposition would make the viewers engage with the photo, i.e. spend longer looking at it. To put it another way, the photo would be far, far more interesting than one of models on a catwalk. Successful (i.e. appealing) photos are ones that people emotionally engage with and spend time looking at, and a juxtaposition can make a photo successful.