The DHT11 is a basic, low-cost digital temperature and humidity sensor. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air, and spits out a digital signal on the data pin (no analog input pins needed).
Connections are simple, the first pin on the left to 3-5V power, the second pin to your data input pin and the right most pin to ground.
Technical details:
Power: 3-5V
Max Current: 2.5mA
Humidity: 20-80%, 2-5% accuracy
Temperature: 0 to 50°C, ±2°C accuracy