Acts as a virtual speaker. Anything you play into it is "sent" through the virtual wire.
After restarting, right-click the speaker icon in your taskbar and select "Sound Settings." You should now see "CABLE-C Input" and "CABLE-D Input" in your Playback list. Common Use Cases vb-cable c d free download
Acts as a virtual microphone. It "receives" the audio played into the input, allowing other apps to "record" it. Acts as a virtual speaker