An ODT file is an XML-based file format designed for storing text documents. ODT files are part of the OpenDocument family of file formats, which also has formats designed for handling spreadsheets, presentations, graphics and formulae. OpenDocument file formats are used by default in the popular office suite software OpenOffice.
While the initial specifications for the OpenDocument file formats were first created by the company Sun, a technical committee in the Organization for the Advancement of Structured Information Standards (OASIS) consortium was responsible for the actual development of the formats.
In addition to OpenOffice, some popular office suites that support OpenDocument files include KOffice, Google Docs and NeoOffice.