OpenDocument Format, or ODF, is a file format used by OpenOffice, the free alternative to Microsoft Word.
The XML-based files are the same as a .ppt or .doc, representing spreadsheets, slide presentations and word processed documents.
ODF files are supported by most office suites, and over 600 companies have ratified the specification.
.odt files are for word processing documents
.ods files are extensions for spreadsheets
.odp files are extensions for presentations
.odb files are extensions databases
.odg files are extensions for graphics
.odf files are extensions for formula and mathematical equations