Related Adobe InDesign or QuarkXPress jobs are often stored in a single job folder with multiple "main" files at the top level and shared resources (such as images and fonts) in subfolders. The Switch configurators for these applications however expect a single main file in each job folder, so these "multi-job folders" cannot be processed without change.
The Split multi-job app splits a multi-job folder in separate job folders, one for each main file. Each resulting job folder contains a single main file, and a full copy of all resources (in fact, everything from the original job folder except for the other main files).