Montage refers to a technique of assembling pieces of separate photographic images into a whole. The intent is to draw connections to previously disconnected images, and assemble a new unity out of disconnected parts.
Montage began with the earliest days of photography, with people cutting and assembling two pictures to make one image. Today, montage can be achieved using high-tech software such as Adobe Photoshop.
Montage always had a populist bent to its themes. While painting required skill and technique, anyone could cut images out of a magazine and glue them together.
The Dadaists in the 1920s became the most famous practitioners of montage. They saw it as a a way to avoid abstractionism without returning to naturalist forms of painting.
Photomontages saw brief revivals in the 1960s when it became infused with pop art, and in the 1980s when it became associated with political activism. Two of the most famous practitioners during these periods were artist Peter Kennard and animator Terry Gilliam.
Montage in film is the assembling of disconnected shots into a greater whole. It's often used to depict the passage of time, though like photomontage, it can also be used to link otherwise unrelated shots thematically.