The Arduino is a microcontroller platform used for building electronic projects. It consists of a programmable circuit board and software to write code. The board contains a microcontroller connected to components and is programmable via code uploaded to the physical board. It functions similarly to a programmable logic controller and was released as open source hardware. The Arduino family includes models like the Uno, Mega, and Mini. Additional functionality can be gained through expansion boards called shields that provide capabilities like motor control, wireless communication, and LCD screen control. Arduino is used in applications such as robotics, automation, DIY projects, and more.