The Pixie control unit sits on the top of the teacher's desk (see images below). It allows for a laptop (or other personal device with an appropriate adaptor) to be connected to the projector via a VGA cable. It also allows for audio to be played over the new speakers via a standard 1/8" audio jack.
The AirPlay device also allows for the transfer of audio and visual data to the projector, except it does so wirelessly! That's right, no more tangled wires. Just a couple clicks of the mouse and your device is seamlessly connected to the projector.