Microcontrollers

Microcontrollers are miniscule, self-contained and simple computers designed to control the functions of embedded system. In essence, they receive input and control output of other devices in the world. For this purpose, they require ports/contact points to receive and express results of whatever process it is designed for.

These manifest as metal pins, with each pin having a specific function (e.g power or communication) ^[1] As microcontrollers are self-contained, they can be considered embedded systems.
Microcontrollers are not the same as microprocessors.