Juxtaposition

Definition of juxtaposition

A placing or being placed in nearness or contiguity, or side by side, often done in order to compare/contrast the two, to show similarities or differences; An absence of linking elements in a group of words that are listed together; Two or more contrasting sounds, registers, styles etc. ...

In simple words we can say that juxtaposition is an image-development strategy used to place, side by side, two or more images or elements in a way that changes the meaning or effect of each.