This picture shows a series circuit. In this circuit the voltage of all the light bulbs is equal to the voltage in the batteries.The voltage in each light bulb is a third of the entire voltage, because the resistance in each of light bulbs are the same, because there are three places where the voltage needs to go. The current in this circuit is the same because the circuit is in a loop, the electrons don't have any where else to go so the current is the same throughout the entire series circuit.
This picture shows a parallel circuit. In this circuit the voltage of the light bulbs are equal, because in a parallel circuit the voltage of each light bulb is equal to the voltage that the batteries produce. In other words the voltage of one of the light bulbs is equal to the voltage in the batteries. If there are only two branches in a parallel circuit the current in the branches is equal to the total current. This is because the total current has to flow through two paths in this scenario, so half goes to one and the other half to the other.
This picture shows a complex circuit. In this circuit there is a series and parallel circuit. Just like the series the current stays the same until the current gets to the parallel part, the current splits and half goes through one branch and the other half of the current to the other. The voltage of the series light bulb is equal to both the voltages of the parallel circuit bulbs. The circuit light bulbs distribute half of the voltage to one and the other half of the voltage to the other.