A VU meter, such as the square box-like area toward the top of the console with the two green horizontal lines (center top), shows the operator the level of sound output. The top horizontal line is the left channel and the bottom line is the right channel.
The audio console converts analog audio (voice via microphone) and phone calls to a digital output. It also allows for the mixing of digital audio from CDs, computers, and other digital sources with the analog audio.
In the case of Internet radio, the audio output would be uploaded to a server which then distributes the audio - or streams it - to listeners.