Touch sensitive led table

Im wondering two things:

  1. What do the infrared photoresistors do? as in how is it used?
  2. What does the infrared led do? and how is it used?

The infrared led & phototransistors are used to do proximity detection.

Im planning to have the photo-resistors take in the serial values, and when someone hovers there hand over the photo-resistor the led light turns on

Where does the serial data come from?

I just want something simple as leds turning on by either motion detecting or light detection.

Light detection = easy. Motion detection is harder as you either need PIR sensors or some other form of machine motion detection that may be beyond arduino's capabilities.

Also is there a way to build something similar to this using photo resistors and leds?

Have a look here Overview | Photocells | Adafruit Learning System

If there are other methods of building something similar to this I would really love to hear your opinions!

Might be worth looking at this http://www.thebox.myzen.co.uk/Workshop/LED_Sensing.html as you could use the LED as the light sensor.