Do you know that computer only understand 2 digits? That digits are 0 and 1, and they are called Binary. When you type any letters or characters in your keyboard, computer does not understand it the way we do. The character you typed will be translated to binary code designated to it. Like for letter “M”, it has binary code of 01001101.
Complicated, isn’t it? But believe it or not, that’s the way it goes. If you are interested on knowing how it works, then try searching for Binary Numeral System. Good luck!