This bar chart shows the populations of the ten most populous countries in 2018, with data sourced from the United Nations World Population Prospects. It illustrates how to customize D3 axes by removing domain lines, styling tick marks and labels, and adding axis titles. The code uses `d3.csv`, `scaleLinear`, `scaleBand`, `axisBottom`, and `axisLeft` to render the SVG, including a custom tick format that abbreviates large numbers into billions.