To have current flow in a circuit there must be a complete path of current from negative to the positive end. When components are connected in series it makes it so that if any one of the components or wires is removed from the circuit, current flow stops completly. Example below with my other image.
Series circuit and path of current:
In this first circuit you can see current can flow from the negative to the positive end freely in a complete loop.
Now with a wire missing:
As you can see here, we removed one wire from one end of the lamp and current does not have a continuous path to flow so you get whats called an open circuit. Your lamp would not light and your circuit would not work.
Now lets take a look at how a parallel circuits. A parallel circuit is one with multiple branches of electricity flow so that if one branch is taken out there is still electrical continuity in the circuit. Here is an example and an explanation.
A parallel circuit and how current flows through it:
As you can see in the above image current flows through all three branches at onces and meets back up at the branch with the light bulb. Now lets break one of the connections and see if we still have continuity
Even with the middle resistors lead broken we still have two complete paths of current flow from the first branch and the last branch.
You can see why you would want your wiring in your house to be in parallel with each other and not in series. Imagine one lightbulb going out and having your house wired in series, the entire flow of electricity in the house would be stopped.
Parallel circuits are nicer and easier to troubleshoot in my opinion. If you have any questions post them in the comments. I will go over how to measure values in both series and parallel in the next post.