There are many different save file formats. Each one allows different accessibilities and allows the content to be placed and seen across many different platforms.
SWF save format allows viewers to view content as an ebook. It makes it a fun and engaging way for work to be displayed. I like the fact that people can actually navigate the pages and click on digital content like youtube clips.
Other formats could be the ordanary InDesign file this allows you to go back in and change the content up or PDF files. These are useful when considering your copyright to the work you produce. It has a creation date and things like that so it protects the content.