When you flip a switch, you close the circuit so now the circuit looks like this: 
Closing the circuit, you connect the wire with the rest of the circuit! But why couldn’t you turn on the light before? Before the circuit looked like this:
Looking at this diagram, we can see that not all of the wires connect to the light, so the light turns off! In your house, it is different because there is not a battery behind all of the light switches! In a house, the battery’ is electricity coming into your house from power wires outside! When the circuit was off it looked like this:
and so the light was off. When you push the switch, the blue part gets connected to the rest of the circuit, giving power to the light, so the light turns on!
Info from Usborne Illustrated Elementary SCIENCE Dictionary
I made a game as well: https://scratch.mit.edu/projects/117102418/#editor
Hi, Paul. I’m glad you are (at least a little bit) interested in electricity. I have a puzzle for you: sometimes you will have a light in your house and TWO switches turn it on and off! (This is called a “three-way” by electricians.) Hmmm. How does that work? I’ll help you figure it out sometime. In this case it’s good to have a diagram to help understand it. Hint: in a REGULAR switch there are two wires: one hot (coming from the source) and one going to the light. In a three-way, each switch has THREE wires coming in or out of it. Good luck figuring out how it works. I’ll help you when you are ready to understand it.
Love, Grampa
I already know! Same as regular, just switch 1 has an extra wire! it goes around switch 2 and joins again after switch 2!
We have a light controlled by three switches.