The group of letters after a period or "dot" in a file name. The extension indicates the format or type of the file. For example, in the file name "readme.txt," the extension "txt" denotes a text file that can be viewed using a text editor, such as Notepad or SimpleText. Operating systems, such as Mac OS or Windows, refer to a file's extension when choosing which application to launch when a user clicks on a file.
For a list of file extensions click here!
NetLingo Classification: Technical Terms