what is a microcontroller or mcu

A microcontroller (MCU for microcontroller unit) is a small computer 
	on a single VLSI integrated circuit (IC) chip. 
A microcontroller contains 
	one or more CPUs (processor cores) 
	along with memory and programmable input/output peripherals. 
Microcontrollers are designed for embedded applications, 	
	in contrast to the microprocessors used in personal computers 
		or other general purpose applications consisting of various discrete chips.