A horizontal bar chart displays the top 10 most populous countries, with population values converted to thousands and formatted with a custom tick formatter that replaces gigabytes with billions. The chart uses d3.csv, d3.scaleLinear, d3.scaleBand, d3.axisLeft, and d3.axisBottom to render axes and bars in SVG. Grid lines extend from the x-axis, while axis labels and a title are added as SVG text elements.