ODT is one of the options for the text file format, which was in little demand and gained relative distribution only in 2014, when Google Docs began to use the ODF format. It takes its name from the OpenDocument Text Document, and is used in office programs that are based on utilities like Open Office or LibreOffice. The open standard ODF (OpenDocument Format) was created by the OASIS community and was intended for the free creation, editing, storage and exchange of office documents. Within its framework, the ODT format also allows the use of databases, presentations, images, tables in text files.
TXT is one of the simplest and longest existing text file formats. The full name of the format is Plain Text File, and the developer is unknown. Text files of this format are very small, and therefore have become very widespread. A TXT file contains text data organized as strings. As a rule, this is a standard text document without formatting. This format is universal, it is available to work in almost any text editor. But one of the simplest and most common is Windows Notepad. Files with the extension .txt are associated with this program by default.