The keyestudio microphone sensor is typically used in detecting the loudness in ambient environment. The Arduino can collect its output signal by analog input interface. 
The S pin is analog output, that is voltage signal real-time output of microphone. The sensor comes with a potentiometer, so that you can turn it to adjust the signal gain.
It also has a fixed hole so that you can mount the sensor on any other devices. You can use it to make some interactive works, such as a voice operated switch.