Step 4: Series vs. Parallel
When things are wired in series, things are wired one after another, such that electricity has to pass through one thing, then the next thing, then the next, and so on.
In the first example, the motor, switch and battery are all wired in series because the only path for electricity to flow is from one, to the next, and to the next.
When things are wired in parallel, they are wired side by side, such that electricity passes through all of them at the same time, from one common point to another common point
In the next example, the motors are wired in parallel because the electricity passes through both motors from one common point to another common point.
in the final example the motors are wired in parallel, but the pair of parallel motors, switch and batteries are all wired in series. So, the current is split between the motors in a parallel fashion, but still must pass in series from one part of the circuit to the next.
If this does not make sense yet, do not worry. When you start to build your own circuits, all of this will start to become clear.