Theory:

We have discussed about electric circuits in the previous section. Let us now discuss the types of electric circuits. Electric circuits are of three types, they are
  • Simple circuit
  • Series circuit, and
  • Parallel circuit
Simple circuit:
A circuit consisting of simple electrical elements like cell, key, bulb and connecting wires is called a simple circuit.
shutterstock_759281488.jpg
Simple circuit
  
The above circuit is simple because it has simple electrical elements like a battery, bulb and switch.
  
Series Circuit
If two or more bulbs are connected in series in a circuit, then that type of circuit is called series circuit.
Current is the same in all the elements in the case of series connection. If any one of the elements is damaged or disconnected, then the entire circuit will not work.
 
shutterstock_1893039766 (3).jpg
Series circuit
  
In the above diagram, all three LED's are connected in the form of a chain, so it forms a series connection. And, the current flow in all the LEDs will be the same.
  
Parallel circuit:
If two or more bulbs are connected in parallel in a circuit, then that type of circuit is called parallel circuit.
Thus, a parallel circuit has two or more paths for the current to flow through. If any element is damaged or disconnected, other elements will work properly without any disruption.
 
shutterstock_1893052531.jpg
Parallel circuit
 
In the above diagram, all three LED's are connected in the form of a parallel connection, so it forms a parallel connection. And, the current flow in all the LEDs will not be the same.
 
Some of the electric symbols:
 
1. Electric cellbattery-161239_1280.png

9.svg
 
2. BatteryStart_Stop_Automotive_Battery.jpg
8.svg
 
3. Switch-open
7.svg
4 (3).svg
 
4. Switch-closed
3 (3).svg
4.png
 
5. Electric bulblight-148483_1280.png
2 (3).svg
 
6. Connecting wires1200px-Romex_cable.agr.jpg
1 (2).svg
 
Reference:
https://pixabay.com/vectors/light-light-bulb-on-bulb-148483/
https://commons.wikimedia.org/wiki/File:Romex_cable.agr.jpg
https://upload.wikimedia.org/wikipedia/commons/8/81/01_-_Set_of_Energizer_Batteries.jpg
https://commons.wikimedia.org/wiki/File:Start_Stop_Automotive_Battery.jpg