An arduino is a could think of it as an itty-bitty, teeny-weeny, yellow You can hook physical things to it, such as lights or motors as well as various kinds of sensors. Using its programming language and programming environment (on a regular laptop/desktop computer) you can create programs that control the various things you have hooked up to the arduino.

The arduino is an example of "open source" hardware where there are no patents or copyrights. If you want to make your own arduino out of the constituent parts, you can do so and actually instructions for doing this are available on The software that allows your computer to send the program you write to the arduino is also open source. The arduino hooks up to your computer via usb.

This video shows the arduino hooked up to six LED (light-emitting diodes), 2 green, 2 blue, 2 red. I programmed the arduino to move through the rainbow by having lights flash in this sequence:
2 red LEDs (Red)
2 red LEDs, 1 green LED (Orange)
1 red LED, 1 green LED (Yellow)
2 green LEDs (Green)

The program controls how long each LED is lit, approximately 1/2 a second for each group of lights. The paper box helps you to see the blended colors by diffusing the light.

Here's the program for this:

The program tells the arduino where to find the lights (7-10, which are the slots in which the lights are plugged in).
An LED is turned on when the program reads "HIGH" and off when it is "LOW."

"Delay" determines the length of time something happens. 500 means half a second.

The first time I hooked up an arduino, it seemed very confusing and as if it took forever. Once you have done a few circuits, it starts to become familiar, more comfortable, and endlessly interesting.