In the late 1800s, some French brothers discovered that with placing enough photographs along a celluloid piece of film they could approximate physical movement
Thus, motion pictures (movies) were born and took off quickly
Most early films were what they called "one-reelers"--that is, a film that lasted as long as the film stock contained on a single reel of film
Then, directors realized they could tell longer stories with multi-reel films but needed a way to do it so they developed a multi-projector set up such as shown here which was the preferred method into the late 1980s