What is the meaning of the prefix letters in the Nikon image file name?

What is the meaning of the prefix letters in the Nikon image file name?

Nikon identifies images taken by using 4 letters at the beginning of the file name and three at the end, with 4 numerical digits in-between, for example DSCN8756.jpg. The first four characters are the identifier, this indicates the type of image. The three characters at the end of  image name are the extension code used by the computer operating system to recognize the file type and open them in the correct program. The four digit number is assigned automatically by the camera in ascending order. Once these numbers reach 9999 a new folder will be created and the numbers will begin again from 0001.

Below is a table with the different identifier and extension codes used by Nikon.