Process Window Index is a way of measuring how well a machine works. It is like a scorecard that tells you how well a machine is working. The higher the score, the better the machine is running. The index looks at a few different things, like the speed of the machine, the accuracy and precision of the results it produces, the amount of energy it uses, and the amount of maintenance it needs. The higher the score, the better the machine is running, so the less energy it uses and the fewer problems it has.