Arduino is an open-source physical computing platform based on microcontroller boards and software. It allows users to create interactive electronic objects by connecting sensors and actuators. Key features include its standard board design, wiring language, and large community of developers. The document provides an overview of Arduino boards and discusses how they can be used to create Internet of Things projects with shields, sensors, and connectivity to platforms like Xively using protocols like MQTT. It also lists several online resources for learning more about Arduino and related topics.