The Difference Between Absolute And Relative Laser Power Measurements

Understanding the difference between absolute and relative laser power measurements is similar to measuring the speed of your car. Do you need to know the exact value in miles or kilometers per hour and take into account any potential error margin, so that you're sure you're not breaking the speed limit, for example? Or do you just need to know whether you're going slower or faster than the other cars around you? The same concept applies to laser power measurement.