Photomontage

Photomontage is the process and the result of making a composite photograph by cutting, gluing, rearranging and overlapping two or more photographs into a new image. Sometimes the resulting composite image is photographed so that a final image may appear as a seamless photographic print. A similar method, although one that does not use film, is realized today through image-editing software. This latter technique is referred to by professionals as "compositing", and in casual usage is often called "photoshopping", due to a particular software often used. A composite of related photographs to extend a view of a single scene or subject would not be labeled as a montage.

https://en.wikipedia.org/wiki/Photomontage