Open Office of which ODT is part of was developed by Sun Microsystems around twenty years ago. The software is open source and is seen as a viable free alternative to Microsoft's Office suite of products. Open Office opens most Microsoft document formats and is is provided as a free download, without restrictions on license. The writer application which produces ODT files is the word processing element of Open Office.
The Open Document Format is an open standard developed by Sun Microsystems under the guidance of OASIS (The Organization for the Advancement of Structured Information Standards). Originally the OpenDocument format was XML based and had at it's root, it now takes the form of a zip file much like Microsoft's DOCX format and takes advantage of the ZIP's compression technology to reduce the overall file size. Writer documents take the form of .odt and .fodt.
Microsoft Office 2007 Microsoft Office 2010 OpenOffice Writer
The .txt file extension is one of the most ubiquitous file types. The file generally consists of plain text only and contains no formatting. Almost any application that can handle text can open a .txt file. As a result this format remains popular due to its support across all platforms and Operating Systems. The file type is one of the oldest file types in existence with its origins tracing back to the first computers.
A .txt file normally uses a basic character set which contains letters, numbers and symbols. A typical example of this would be the ASCII character set. The main alternative to ASCII is Unicode. Unicode is a rival format for text files. A plain text file should only contain several non-printable charaters such as new lines, tab and form feed.