This is an Arduino Carbon Monoxide Sensor. It uses MQ7 probe to detect Carbon Monoxide (CO) concentrations in the air from 20 to 2000ppm.
The sensitivity can be adjusted by the potentiometer. The output is proportional to the density of gas. You can use analog reading to read the data from this sensor.
To ease the difficulty of using this sensor, a Gravity Interface is adapted to allow plug&play. The Arduino IO expansion shield is the best match for this senor connecting to your Arduino microcontroller.