Basically there are two distinct types of circuits those that are connected in series and those that are connected in parallel. Series circuits are those that have circuits or components connected to each other consecutively that is one after the other. A circuit that has two light bulbs and a battery along with wires will have the power cord going from one lead of the battery to one of the bulbs, from this bulb to the next and from there back to the battery. Here the bulbs are not connected individually to the battery but in series one after the other. In a circuit that is a circuit in parallel these bulbs would have individual leads leading up to the same battery. Because of the fact that the current has to flow through every element of the circuit and this means that the current all through out the circuit is the same.