The key ideas for series and parallel resistors follow from the behavior of the current and voltage through each configuration.

For PARALLEL RESISTORS , the VOLTGE across each resistor is the same.

It's the current that will divide up between resistors. Whatever current that passes through the whole configuration will divide between parallel resistors. So, for the circuit shown here, a current flows through the whole configuration. ALL of that current flows through the one resistor on the left. Then the current divides and passes through the two parallel resistors on the right. The voltage across the parallel resistors will be V = i R. "i" is less through each parallel resistor than it is through the one series resistor. If the R's are all the same, there will be a larger voltage drop across the left resistor, and smaller voltage drop across each of the two parallel resistors.