A horizontal bar chart shows the top 10 most populous countries, with population values on the x-axis. The chart customizes the x-axis to format large numbers as billions (e.g., "1.42B") and removes the default axis lines and domain. It uses D3's `scaleLinear`, `scaleBand`, `axisBottom`, `axisLeft`, and `format` to handle scales, ticks, and number formatting. Data is loaded from a CSV file, and the SVG rendering is set up in `index.html` with `styles.css` controlling visual styling.