|A sound sensor.|
There are 4 clearly marked pins; +, G, AO and DO. + and G are clearly +5V and GND. AO and DO maybe stand for Analog Out and Digital Out ?
I used the tutorial code from the arduino website, but the sensitivity of the device seemed too low to be exciting. I had to bang it on the table, or scream into it, to get any result. So I abandoned this sensor as fairly useless for any of my requirements. If it was recording a sound and playing it back then I would have had more fun with it !