In a simple circuit the the current at every point is equal. That means the amount of charge leaving the power source is equal to the amount charge entering and leaving a resistors, and equal to the amount of charge returning to the power source.

For any circuit regardless of it configuration is that the voltage at the power source is equal to to all of the potential consumed by the resistors.

example: In the diagram above the potential at the power sources is 12 volts. As the current travels through the resistors (R1, R2, and R3) those 12 volts are consumed by the resistors. If the resistance in each resistors is the same then each resistors consumes their fair share (4 volts each). If each resistors different, then each resistor consumes their percent of there total resistance (if one resistors makes up 50% of the total resistance then it would consume 6 volts while the other two have share the remaining 6 volts)