Document file format is a text or binary data file type used to store formatted documents including texts, pictures, cliparts, tables, charts, multiple pages, multiple documents etc. There exist a multitude of incompatible document file formats today.
The most known document file extensions are e.g. documents created by Microsoft Office suite like doc, docx (created by Microsoft Word documents), xls, xlsx (Microsoft Excel spreadsheets) and ppt, pptx (Microsoft PowerPoint presentations).
PDF (Portable document format) file format is developed by Adobe Systems and is a standard documents for user to read, but not edit. PDF format has become as ISO standard in 2001 and is widely used today.
Competition for Microsoft Office document formats is OpenDocument Format (odf file extension) used in open source suite called OpenOffice.org and its clones. The OpenDocument Format is an open XML-based document file format for office applications to be used for documents containing text (odt file extension), spreadsheets (ods file extension), presentations (odp file extension), and graphical elements (odg file extension).
Mostly used open international standard is HTML (HyperText Markup Language) files, which could be also used as document file format.