Before we can answer this question, we must learn the relationship between a few other technical terms. We'll use the classic "highway" analogy to convey a general idea of how electrical current flows. Let's review a few terms you're sure to have heard before:

Voltage- Think of voltage as the amount of lanes, or intensity of the electricity moving through the wire.

Current- Current would be relative to the speed of the cars, or electricity.

When we multiply these figures, we get a result measured in Watts, or final output.

So where does impedance factor in? In a nutshell, impedance is a figure that represents how much current applied at one end of a line will make it to the other end. Think of impedance as whatever would cause traffic to move slower on a highway; everything from potholes, to construction zones. This leads to inefficiency, which translates to excess heat in electrical terms. The lower the resistance, the more efficient it is at carrying signal; meaning in an optimal scenario, 50 ohm cable would perform better than 75 ohm.