The Raspberry Pi is a computer more than a microcontroller. It runs an operating system (i.e. - Linux) and connects to audio, video and more. Though it can be used to control physical computing components like other microcontrollers, the Raspberry Pi is different in that it has an applications processor and not a microcontroller.
The Raspberry Pi runs on a Linux operating system, and can use keyboard/mouse inputs and outputs to a display (via HDMI).