Writer file types in Save dialog

ODF Text Document (.odt) This is the default format for LibreOffice. It is a completely open format that many other word processors can read and write to. It is not tied to a particular word processor, but it is designed to be shared across applications and platforms.
ODF Text Document Template (ott) This is the default template format for LibreOffice Writer. It contains the page layout and default styles for a text document. Like .odt it is not tied to a particular word processor.
Flat XML ODF Text Document (fodt) This is the ODT file stored as a Flat XML file rather than the .ZIP.
Unified Office Format text (.uot) This is the Unified or Uniform Office Format that was developed as an open Chinese format. Like ODT, it uses XML to describe documents, but it is not directly compatible with ODT.
Microsoft Word 2007-2013 XML (.docx) This is the standard format used by Microsoft Word 2013, 2016, and 2019. Writer can read and write to this format. It also is known as ISO/IEC 29500 Transitional. This is an XML format released by Microsoft that is an open standard, but not as open as ODT.
Microsoft Word 2003 XML (.xml) This is format is a successor to DOC and a predecessor to DOCX. It is an open format that allows you to extract data from a document. It was a standard format in Office 2003.
Microsoft Word 97-2003 (.doc) This is the old, proprietary, binary format that was central to Microsoft Word for years.
Microsoft Word 97-2003 Template (.dot) This is the old, template format for Word. It stores styles and layout information.
DocBook (.xml) The schema has been under develop since 1991. It was designed for books and papers, particularly about computer hardware and software. This allows Writer to be an excellent tool to create technical manuals.
HTML Document (Writer) (.html) Writer documents can be saved as standard Web pages.
Rich Text (.rtf) This format was developed by Microsoft in 1987 to allow documents created in non-Microsoft applications to be compatible with Word.
Text (.txt) This format is for creating documents with unformatted text. Most applications can open documents in this format.
Office Open XML Text (.docx) This is the format Microsoft submitted to various standards committees as an open format, known as ISO/IEC 29500 Strict. Writer can save in this format. This format does not support backward compatibility in Word, so it is not its default format.
Microsoft Word 2007-2013 XML VBA (.docm) This is the transitional Office Open format that supports macros. Writer can create macros that will work in Word, as well as itself.