GSCOUTGPS : What is MSDC and PCAM USB modes?

MSDC - Mass Storage Device Class 

This setting allows to transfer your files to your computer as if the camera is a Card Reader. 

In Windows Explorer your camera will appear as an external storage device for file transfer.

PCAM - Computer Video Camera

This setting allows to transfer your files to your computer as if the camera is a PC Camera. 

In Windows Explorer your camera will appear as a camera and you will be able to import your videos and pictures.