The OpenDocument Format (ODF) is an open XML-based document file format for office applications to be used for documents containing text, spreadsheets, charts, and graphical elements. The file format makes transformations to other formats simple by leveraging and reusing existing standards wherever possible. As an open standard under the stewardship of OASIS, OpenDocument also creates the possibility for new types of applications and solutions to be developed other than traditional office productivity applications.

Source: Oasis Open Technical Committee