Rich Text Format

Rich Text Format (RTF) is an interchange file format originally developed by Microsoft in 1987 for the exchange of documents between Word and other document preparation systems. It retains text formatting which plain text files do not.

Rich Text Format with attachments
RTF files can be read by TextEdit, which is included with Mac OS X and macOS. It can also include images and media with RTF files by encapsulating them in a package format identified as rtfd, an abbreviation for Rich Text Format Directory. Other operating systems that are unable to interpret bundled or packaged data, such as Linux and Windows, will present the RTFD data as an ordinary folder.