DOC is the document file format established by Microsoft Word and uses the .DOC file extension. Next to text, these files can also contain hyperlinks, images, graphics, tables, advanced formatting, and other elements.
With Microsoft Office, 2007, the .DOCX file extension was introduced. It uses the Microsoft Office Open XML international standard which makes the format more accessible and usable.
While newer versions of Microsoft Word can open the old DOC format, DOCX files cannot be opened in older versions. If they can be opened, it is possible that the formatting is offset or that parts of the document are missing.