In this project, you're going to create a sound-activated switch. The switch turns on and off an LED, but you could modify the project into controlling other things too (just ask if you need guidance).
The sound sensor is a small module with a microphone, amplifier and some small circuitry. It has two outputs; one digital and one analog output.
The digital output is either high or low, depending on if the sound level is above a threshold or not. You can adjust the threshold with the potentiometer on the module.
For this project, you're going to use the digital output.