Light sensors are probably one of the most common sensors in life, they can be found in your laptop, phone or home lighting system. A light sensor measures the level of light in a room or ambient light in a space.
This module uses a special ambient light detector(MET6000) with a spectral response that closely emulates the human eye. It helps you to detect the light density and reflect the analog voltage signal back to the Arduino controller. You can set the threshold of voltage level to trig other units on the Arduino project.