The Arduino Yun is an Arduino board with WiFi built-in, allowing users to connect their sensors and buttons to the Internet of Things (IoT) without the need for a separate WiFi shield. The board comes with a second microprocessor running a lightweight version of Linux and Python preinstalled. To get started, users must prepare an SD card, upgrade OpenWRT, connect to a WiFi network, SSH into the Yun, and install the Arduino IDE on their computer. Once set up, users can write Python scripts that trigger LEDs, motors, and other actuators. The board also has three buttons for resetting the WiFi settings, Arduino chip, and Linux chip. Users can use the Yun to build projects such as a photo booth, send SMS and MMS messages, or even teach their dog to text selfies.