A horizontal bar chart displays the top 10 most populous countries, with population values formatted in billions using d3.format and custom tick labels. The chart uses d3.scaleBand for the categorical y-axis and d3.scaleLinear for the numeric x-axis, with axisBottom and axisLeft generating grid lines and labels. Bars are rendered as SVG rectangles, and axis labels and titles are added as SVG text elements, styled via external CSS. Data loads from a CSV file using d3.csv.