"So... imagine that someone enters a kitchen, because they want to show you how to make a cup of coffee. As you watch carefully, they flick a switch on the wall

"So... imagine that someone enters a kitchen, because they want to show you how to make a cup of coffee. As you watch carefully, they flick a switch on the wall. The switch looks like a light switch, but none of the lights in the kitchen turn on or off. Next, they open a cabinet and take down a mug, set it on the worktop, and then tap it twice with a teaspoon. They wait for thirty seconds, and finally they reach behind the refrigerator, where you can't see, and pull out a different mug, this one full of fresh coffee. ...What just happened? What was flicking the switch for? Was tapping the empty mug part of the procedure? Where did the coffee come from? That's what this code is like." This is such a good metaphor