Explain · Like I'm five version
Series and parallel circuits in terms of roads and roundabouts
An electric circuit is just a busy road for tiny invisible cars called electrons.
In a series circuit, every car has to drive down one long, single lane to get to the end of the street. If a single pothole closes that road, every car stops moving and no one gets home. It is like a conga line of little buses that all have to move together, or else the whole school trip is stuck behind a broken gate. You cannot add a new stop without making the path longer for everyone else, which is why your Christmas fairy lights all go out when one bulb decides to take an early nap.
A parallel circuit is much better because it works like a giant roundabout with lots of different exits. Each little car can choose its own special road to reach the house or the lamp, and they do not have to wait for the others. If one road gets blocked by a grumpy tractor, all the other cars just zoom along their own paths as if nothing happened. This is why your bedroom lamp stays on even when you unplug the TV in the lounge, because the electricity has plenty of other ways to travel.
It is a clever way to keep things running smoothly, just like a well-planned set of streets. You can keep adding more homes to the roundabout without slowing down the traffic, provided you have a big enough power station to keep the cars zooming. It keeps the whole city of your toys and gadgets happy and bright.
Where the analogy breaks downelectrons do not have drivers and they do not stop to look at scenery.