doc
Files with .doc extension represent documents generated by Microsoft Word or other word processing documents in binary file format.
The extension was initially used for plain text documentation on several different operating systems.
It can contain several different types of data such as images, formatted as well as plain text, graphs, charts, embedded objects, links, pages, page formatting, print settings and a lot others.
The format was popular for all sorts of documentation due to the variety of options it offers to users for writing manuals, proposals, specifications, resumes, articles or any similar documents.
The updated version of DOC is DOCX which is based on Office OpenXML whose specifications are openly available.
odt
ODT files are type of documents created with word processing applications that are based on OpenDocument Text File format.
These are created with word processor applications such as free OpenOffice Writer and can hold content such as text, images, objects and styles.
The ODT file is to Writer word processor what the DOCX is to Microsoft Word.
Several applications including Google Docs and Google’s web-based word processor included with Google Drive can open the ODT files for editing.
Microsoft Word can also open ODT files and save it in to other formats such as DOC and DOCX.