Here are some other examples of file extensions.

.exe (An executable file, usually the file that starts a program.)

.pdf (Portable Document Format, is a file format created by Adobe Systems. Most office documents come in .pdf file format.)

.zip/.rar (These could be any file but they have been compressed and packed away to a smaller size. When unpacked or unzipped it will become what it was originally.)

.wav/ .mp3 (Music files)

.jpg/.gif/.bmp (Picture file formats)

To show file extensions:

1. Open any folder on your computer.
2. Choose "Tools" - "Folder Options".
3. Click the "View" tab.
4. Uncheck "Hide extensions for known file types".
5. Click "OK" to close the dialog box.