Area Charts are usually used when it is necessary to demonstrate a volume of something that changes in time continuously - for example, a birth or divorce rate, a volume of some liquid or other. It looks like a Line/Spline series with the area between the Line/Spline and the X-Axis colored.
A 3D Area Chart is a kind of Area Chart, it uses standard two-dimensions coordinate system, no third axis in the third dimension is used, it is called so because of some volume of the colored area itself. So, the only difference is in chart's appearance.
This Chart demonstrates how the ACME Corporation shares' prices changed each day during September 2015. The Y-Axis holds the values in dollars, from 0 to 75, and stands for the share price. The X-Axis is responsible for the date. Tooltips show the date in the title and the ACME Corp. share price in the tooltip body. Both x-oriented and y-oriented grids are enabled, so it is easier to watch the points. Each point on the chart can be selected, as well as several points (press and hold the Ctrl or Shift key (for Win OS)).
The feature shown on this chart is making a 3D chart out of 2D by using the area3d() method.