The Open Document Format for Office Applications (ODF), also known as OpenDocument (OD), is an XML-based file format for spreadsheets, charts, presentations and word processing documents. It was developed with the aim of providing a universal document format that could be used with any office software suite.
The standard was developed by a technical committee in the Organization for the Advancement of Structured Information Standards (OASIS) consortium. The specifications were originally developed by Sun Microsystems as an XML format for OpenOffice.org office suite.
In addition to being an OASIS standard, version 1.1 is published as an ISO/IEC international standard, ISO/IEC 26300:2006/Amd 1:2012 - Open Document Format for Office Applications (OpenDocument) v1.1.
Read more about OpenDocument: Specifications, Standardization, Worldwide Adoption