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.
TXT is a file format that contains the text, organized in rows. Text files opposed binaries that contain data that is not intended for interpretation as a text (encoded sound or image). The text file can contain both formatted and unformatted text. Since the very simple text files, they are frequently used for storing data.