Photomontage is an artistic practice that has endured almost since the birth of photography itself. At its most basic level, the photomontage is a single image combined of two or more images.
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 the final image may appear as a seamless physical print. Its a montage constructed from photographic images and uses the technique of constructing a photomontage.

My response:

Why is photomontage important?

It was first used as a technique by the Dadaists in 1915 in their protests against the First World War. It was later adopted by the surrealists who exploited the possibilities photomontage offered by using free association to bring together widely disparate images, to reflect the workings of the unconscious mind.