Make a circuit of a bulb, two batteries (placed against each other and in the same direction) and two wires.

When the bulb is alight, pull the batteries apart. The light will go out. Push them back together again and the light will come on.

Take the bulb out of the socket. The light will go out. Put it back in again.

Take one wire off the end of the bulb. The light will go out. Put it on again.

All of the things you have done make a break in the loop. Circuits only work when there is no break.

So what you have done is to show how switches work. It's just that switches are much more convenient to use than connecting and disconnecting wires.