This stacked bar chart compares the religious composition of populations across fifteen countries, using data from a CSV file. Each country is represented by a bar, segmented into colored layers for different religions, with population sizes on the y-axis. The visualization uses D3 v3 with `d3.layout.stack` for stacking, `d3.scale.ordinal` and `d3.scale.linear` for scales, and `d3.legend.color` for the legend. Hovering over a legend item highlights that religion’s segments, and a tooltip displays population values.