Good thing we learned about circuits because physics is all over Christmas lights. have you ever tried lighting up your Christmas tree and notice that some lights light up and others don't? well this is because the lights are in a parallel circuit. this means that the electrons are shared between each light and have to go to each light separately. so when one light goes out only that one light goes out and not the rest. in a series circuit its the opposite because the electrons have to move through every light and if one light is broken then that means all the lights are not going to shine. this happens because you cant have a circuit with a open loop in it since the current cant jump.