This line chart shows population over time for different world regions, with a vertical line marking a selected year. Users can hover over the chart to change the selected year, which adjusts the line's position. The visualization uses D3.js v5 to render SVG elements, including a color legend, axes, and multiple line paths. It also employs D3's scale functions, line generator, and mouse event handling to update the chart dynamically based on the United Nations population dataset.