A horizontal bar chart displays the populations of ten countries for the year 2000, loaded from a CSV file via a custom `useData` hook and `d3.csv`. React renders SVG bars whose widths are scaled by `d3.scaleLinear`, while countries are positioned with `d3.scaleBand`. Axis components generate ticks and labels using `d3.format` to abbreviate numbers. Hovering reveals native SVG tooltips with formatted values.