Photoresistive light dependent resistor module. Keyes brand KY-018. This module allows for easy sensing of light levels from within your micro controller application. Just connect GND and VCC to the module and a varying voltage depending on light level is available on the third pin.
Please Note: The screen print on these modules is incorrect. The correct connections are as follows:
Pin 1: VCC
Pin 2: GND
Pin 3: VOUT