This sensor is the DHT-22 which senses the temperature and relative humidity of the surrounding air. The DHT-22 is pre-calibrated at the factory, with the calibration information stored in an 8-bit computer inside the unit.
Air temperature is measured in Centigrade, with a range from -40 to +80 degrees and an accuracy of 0.5 degrees. Relative humidity is measured as a percent, with a range of 0 - 100% and an accuracy of 2 - 5%. A downside to this sensor is the sampling rate - measurements are can be taken once every two seconds at most.