Electrical resistance (measured in Ohms) is a measure of how much current will flow through a circuit for a given voltage. It is the reciprocal of conductance. A related property is electrical resistivity, ρ which is property inherent to the material, given by

$ \rho = R \frac{A}{L} $

For DC circuits, resistance is related to voltage and current by Ohm's law,

$ V = IR $

For AC circuits, it is the real part of impedance.