The Plot Area for a chart is the layer or a backdrop upon which the chart itself is placed. This layer has axes on its perimeter and also, the Data Series and Gridlines are placed above this layer. By default, the Plot Area has no fill attributes, and thus it shows the slide’s background. This may look plain, and that by itself is no reason to change the fill of the Plot Area. However, there are times when the slide background itself is busy — and adding a different fill to the Plot Area can then make the chart appear more clear.