Since 2007, Microsoft began to use a file format docx, which is created by using the Office Open XML. The format is a zip-file containing the text in the form of XML, graphics and other data that can be translated into a sequence of bits using patent-protected binary formats. At first it was assumed that this format will replace the doc, but both formats are still used today.
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.