Here is some example code taken from the Arduino IDE which makes the led of the Microcontroller blink.
What is a microcontroller? Its like a mini personal PC, controlling features of a larger component, without an Operating System. It contains a CPU,memory and input/output devices where it can send and receive signals.
Microcontrollers also have ADCs and DACs, an ADC being a Analog to Digital Converter. It converts an analog signal, which consists of sine waves into a digital signal, denoted by square waves. The digital signal represents information as a series of binary digits (1 or 0).
If you have a 1 or 0 depends of the voltage grade and which ranges you decide to assign to which number. Most of the time 0 represents a lower voltage range than 1. If you want to play around with microcontrollers, they are quite cheap, like eg. 10 Euro.