A file extension is the last section of a file name that typically defines the type of file (for example, .JPG and .EXE). Windows defaults hides file extensions. In order to show the extensions in your Explorer views, you have to unhide them by doing the following from My Computer or Explorer.

1. First click on any folder.
2. Click onTools, and then Folder Options.
   
   
   
   
3. Click on the “View” tab and make sure that the “Hide extensions for known file types” is not checked.
   
   
   
   
4. After this click Apply and ok to close the window.