A file extension is a suffix at the end of a computer file's name that indicates the file's type or format. It usually consists of three or four characters following a period (dot) in the filename, such as .txt, .jpg, or .exe

. This extension helps the operating system and users identify the kind of data stored in the file and which software program should open it. For example, .txt indicates a plain text file, .jpeg signifies an image file in JPEG format, and .docx corresponds to a Microsoft Word document

. File extensions serve as metadata that convey how the data inside the file is organized and what application is associated with it. They are essential for the OS to correctly open and handle the file

. Some extensions are specific to certain programs or file types, while others may be used by multiple applications, leading to occasional conflicts

. In summary, a file extension:

• Is the part of the filename after the last dot.
• Indicates the file format and type.
• Helps the operating system associate the file with the correct program.
• Typically consists of 2-4 characters but can be longer.
• Is widely used to identify text, image, audio, video, executable, and many other file types