This example uses a bar chart to illustrate data joins in D3.js, showing population figures for nine countries from a CSV file. The bars are rendered as SVG rectangles, with their heights mapped through `scaleBand` and widths through `scaleLinear`. The code loads data with `d3.csv`, converts population values to numbers, and appends rects via `selectAll().data().enter()`, demonstrating the fundamental enter selection pattern. The chart itself displays the sorted country population distribution, with China and India leading by a wide margin.