RTF (Rich Text Format)

Stands for "Rich Text Format." RTF is a file format standardized by Microsoft for creating formatted text files. Unlike a basic text file, an RTF file can include information such as text style, size, and color. The nice thing about the RTF format is that it is a universal format, meaning it can be read by nearly all word processors.

File extension: .RTF

Definition from the Tech Terms Computer Dictionary
http://www.techterms.com/definition/rtf