Simple Node that sets the gain level (volume) of an Audio line. When used with a Control line, it basically acts as a multiplier. This Node is functionally identical to the Multiply Node .
Audio and Control lines (visualized with blue and purple, respectively) are both analogous to an analog signal. They can be used interchangeably, and, for example, an Audio output (blue) can be connected to a Control input (purple), or vice-versa.