Photo collage has a rich history of artists using photographs and other materials in various ways to put together images as a single piece of art. There are specific styles and many of them cross over to other processes.
Some artists make photographs, using them like paint and collaging a larger narrative out of many parts. As an example, they might go out into nature and photograph various tree textures, flowers, landscape scenes, and other objects. They use those photographs and manipulate them digitally, making a collage with software or they might print them and work on a more physical level with something adhesive.