is a format developed by Sony for its proprietary Sony Reader devices. Files in this format may contain text and images. The format is XML-based.
HTML is a Web format file. HTML source code can be changed in a text editor. HTML files are being developed for future use in the users web browser, allowing you to format text, images and other materials required sites. File with this format use tags to build web pages. HTML code is parsed Web browser and usually not visible to the user.