A horizontal bar chart displays the top 10 most populous countries using data from a CSV file, with population values formatted in billions. The chart uses `d3.scaleLinear` and `d3.scaleBand` for positioning, and customizes both axes by removing domain lines, adding grid lines via `tickSize`, and applying a tick format that converts G to B. The left axis labels are positioned with `d3.axisLeft`, while the bottom axis uses `d3.axisBottom`.