is a format developed by the International Digital Publishing Forum. It is characterized by the XML- and XHTM-based optional use of CSS styling. The main feature of this format is the use of reflowable text (word wrap) which makes it possible to adapt the image to different device displays. The ePub file is a zip-archive with an .epub extension.
XLSX is a file format created with Microsoft Excel, version from 2007 and younger. This file is a spreadsheet. All data distributed document and stored in the cells. Each cell has a unique address, which is denoted by the letters and Arabic numerals. XLSX file format is based on the Open XML. To reduce the size of the file is compressed ZIP.