The DOCX file format is used by Microsoft Word 2007 and later. It is based on Open XML, meaning it is saved as text document rather than a binary file. DOCX files also incorporate ZIP compression to reduce the file size.
About Microsoft Word
Word is a popular word processor for Windows and Macintosh computers. It is that standard word processing program used by most businesses and is also popular among consumers. Word supports advanced text styles and page formatting, as well as images, charts, and graphs. The program also includes a "Track Changes" feature, which allows other users to edit Word documents and note each change they make.