This line chart shows UN population estimates and projections from 1950 to 2100 for world regions, with a vertical black line marking the currently selected year. Users can hover anywhere on the chart to update the selected year, which is highlighted by the line. The visualization uses D3 v5 with d3.nest() to group data by region, d3.scaleTime() and d3.scaleLinear() for axes, and SVG line paths with a curveBasis interpolation. A color legend and axis labels are also rendered, with data loaded from two CSV files.