Superimpose is a term used to describe the process of placing one image or object over another. It can be done in various ways, such as covering, encasing, overstriking, and overlaying. Covering involves placing one image or object over another, encasing involves completely surrounding the object with another, overstriking involves placing one image or object on top of another, and overlaying involves placing one image or object on top of another without completely covering it. All of these processes are used to create a composite image or object.