File extensions are groups of letters following file names. Between the file name and the file extension is a “.”. This file extension indicates what the file format is. For instance, Microsoft Word documents have a “.doc” following the name of the file. Once you become familiar with some of the common file extensions, by seeing the file extension of “.doc” you will know that it is a Microsoft Word document.
While it is helpful for people to be able to recognize the file extensions, the primary purpose of file extensions is actually for computers. File extensions allow operating systems to identify what software program it needs to use to open the file.