ELI5: Explain Like I'm 5

Key punch

Key punching is like playing a game where you type on a computer, but instead of typing words, you punch holes in a piece of paper. And each hole you punch corresponds to a different letter, number, or symbol. Once you have punched all the holes in the right places, you have created a message that the computer can read. It was a way of getting information into the computer before we had fancy keyboards like today!