So can we say that they have the following applications or there are other main applications than these,,,
1) Christmas Light strings - the little bulbs are in series.
2) Batteries in the remote - they are in series, say 4 pieces X 1.5V = 6Volt
3) A Voltage Divider - 2 resistors in series, across one of them you get a desired voltage (which is smaller than the total voltage).
Parallel circuits:
1) A Chandelier - all the light bulbs are in parallel.
2) Everything in your house - all appliances are in parallel to the mains supply.
3) A Power divider - 2 resistors in parallel, which share the power dissipation (heat).