Answer:
In a simple parallel circuit -- for example, two resistors in parallel with a voltage source -- the voltage across the terminals of each component is the same. The current, however, 'splits' in order to take the two separate paths. In this case, you would use Ohm's law to find the current through each branch. In other words:
I1=V/R1, I2=V/R2.
If you have a current source instead of a voltage source, you would use current division to calculate current:
I1=Isource*R2/(R1+R2), and I2=Isource*R1/(R1+R2).
This is all in contrast with a simple series circuit, in which the current is the same through each component but the voltage drops are different. In which case you would use Ohm's law or Voltage division to calculate the individual voltages, depending on the source.