The USB CDC driver for Atmel SAM ARM microcontrollers allows a USB microcontroller that is running the SAM-BA software to be configured as a virtual COM port on a PC.
This allows user software to be loaded to the microcontroller via a USB cable using the SAM-BA PC application software.
The article on Installing the SAM-BA USB CDC Driver for Atmel ARM Microcontroller in Windows shows how to install and test the driver.
Terminal emulator software is used to communicate with the embedded SAM-BA software on the microcontroller and request the SAM-BA software version number. This is done to test that the driver and connections are working properly.