Here are the main rules:
One Path Only - In a series circuit, there's only one path for the electricity to flow.
Same Current - The same amount of electric current flows through each part of the circuit.
The voltage (like pressure pushing the electricity) adds up as you go around the circuit. So, if you have three light bulbs in a series, the voltage across each bulb adds up to the total voltage of the battery. IN other words the voltage of the battery is shared across the componets in the circuit.
If one component (like a light bulb) goes out in a series circuit, it breaks the path and stops the flow of electricity.
So, in a series circuit, everything is connected in a single loop, and if one part stops working, it affects the whole circuit.