In certain applications or contexts of those applications, the user may want to zoom in a section of the chart to view in more detail such information. Instead of specifying a Zoom factor to the chart, you are able to select a region to be zoomed.
When pressing this button you can select a region in the chart to be zoomed. For example in the following conic chart we will be zooming a portion of it:
In order to deactivate the zoom factor, just press the zoom button again and the chart will return to its normal view.