A microcontroller is a small low cost system with a processor, memory & peripherals that can be used as an embedded system. Microcontrollers are used today are embedded lots of products & machinery some common examples include mobiles, vehicles and almost all day to day required household equipment. Using micrcontrollers you can interface Input and output devices like relays, solenoids, latches, LCD display, switches, and sensors like light, temperature humidity, water level, various gas sensors etc.