Stacked Area series is a good choice when you need to demonstrate several dependencies of the same kind: several functions of some volume are drawn one over another, forming a whole volume together. It is usually used to show changes in an amount of something in dependency of time or any other variable.
3D Chart is a modification of 2D Chart. It does not have an additional Z-Axis, forming a third dimension, it only looks volumetric. So, the difference is in the chart’s appearance. You can make a chart in 3D instead of 2D by using the area3d() method.
This particular 3D Area Chart shows the revenue ratio got from 10 cosmetic products sales in 4 states: Florida, Texas, Arizona and Nevada. The Y-Axis values are given in percents from 0 to 100, and the whole revenue percentage volume is taken as 100%, so each value is counted as a part of a whole. Tooltips on the chart are unified, i.e. in “union” mode, and they show values in dollars, not in percent, as you can match them with the Y-Axis values to see the ratio. The legend in the chart is enabled, so you can hide and show the series back if necessary. Note that all enabled series form 100%, no matter how many of them are enabled.