Arduino is an open-source hardware and software platform for building interactive electronic projects. It consists of a programmable microcontroller board and IDE software to write code. The board contains ports that can be configured as digital or analog inputs/outputs to interact with sensors, LEDs, motors and other components. Common Arduino boards include the Uno, Nano, Mega and Leonardo, which differ in processor, memory and I/O pins. The ATmega328P microcontroller on the Uno uses a Harvard architecture with separate memory and buses for instructions and data, allowing simultaneous access.