What is the type for?

What is the type field for?

The type field lets the program know what type of file it is signing.

If you select Main Program, the program is added to the main programs database. And in the future you will sign it by choosing it from the program drop down menu.

If you select to Sign when signing * (with * being a program name)

 every time you select the main file from the program drop down menu this new file will also be signed.