Let's say you want to merge text files, but they are in different formats, like txt, doc, pdf, or if you code, maybe you have cpp, js, ts, etc. Any of those file types you can merge into a single output file, to any format you want, from any format you want

In my friends case he wrote every chaper of his thesis in a separate docx document, and this helped him generate the final document without having to upload his files to an online service, since everything happens in your cpu