The Arduino UNO (Figure 1) is the latest version of the basic Arduino board, and you need one of these to follow this article (see Resources for the UNO's detailed specifications).

An Arduino is a popular open-source single-board microcontroller. Learn how to program one and let the possibilities take shape.

Windows/Mac/Linux: Programming an Arduino isn't especially difficult, but if you're looking for a more visual method, Scratch for Arduino (S4A) uses MIT's Scratch as a groundwork for teaching kids ...

In one of the lowest spec examples of the last one, [gvl610] has got an up-to-date Linux kernel to boot on a vanilla Arduino Uno.

Arduino microcontrollers have added Python to the range of compatible programming languages. Others can be used, and not just Arduino's own IDE app.