A 50-amp breaker uses four wires, two of which are hot feeds of 120 volts. This results in 50 amps at 120 volts for each leg.
Voltage is the measurement of differences in electric potential energy. Amps measure the current or how much electricity something is using. Using the proper voltage to handle the amps is important because it is the vehicle that voltage pushes through a wire. The wire is like a bridge and it needs to be able to handle the demand of the amps and voltage or else it fails to power the appliance or other electrical component.