What does MAD refer to?

It refers to Mean Absolute Deviation. It is the sum of errors divided by the sample size. It can be used in evaluating the accuracy of demand forecasting method by summing the differences between the actual demand and the forecast demand then dividing by the sample size. It is more convenient to use than the other method of evaluating the accuracy of forecasting method, which is Mean Squared Error (MSE). MSE is calculated by taken the sum of squared errors divided by the sample size. MSE uses the squared errors, which can enlarge the error values unnecessarily.