The page descibes how to choose video and audio devices which you want to use for capturing video and audio.

Video Capture Device:
Lists the available capture devices you can use for capturing video. If you only have one video capture device attached to your computer, that device is the only one listed.
For many video capture devices, the name of the device is listed according to the hardware manufacturer’s name and device name.

Click to learn and set the properties of the chosen video capture device.

Audio Capture Device: is disabled in the version 4.0
Lists the available audio capture devices you can use for capturing audio. If you have only one audio capture device, such as your default sound card, that device is selected automatically.

Click to learn and set the properties of the chosen video capture device.

See next:
Capturing video