I had the same struggle with an identical sensor from RobotLinking. I discovered that the - next to the left pin is for the ground, the middle pin is for the 3.3V or 5V (this sensor apparently can do either), and the right pin, marked S, is for the sensor's output. I have a sensor set with 37 sensors, most of which are like this.
As for what this board does, from the best I can tell:
- It's a temperature sensor
- It has an integrated LED to show when you are reading the temperature
- It has a resistor built into it, so no need to use a resistor to protect your controller.