This is a tiny analog proximity sensor. It combines an infrared LED emitter with a infrared phototransistor to detect a reflective object from about 1/2" away to almost zero. It can also be used a (bright) ambient light sensor.
The on-board components drive the LED emitter and bias the phototransistor output to the Vcc level (high) with zero light, and the stronger the reflected (or direct) light signal, the lower the voltage will go, to near-zero at full saturation.
The PCB connection is silk screened on the reverse side, and the convenient "hobby servo" pinout of: Signal-Vcc-Ground.
As with most of our boards, we don't install or include headers or plugs, since the choice will vary greatly depending on the application and personal preferences. The are available (at a very low cost!) in the "Headers & Plugs" category.