This bar chart displays the population of the top 10 most populous countries, based on 2018 estimates from the United Nations World Population Prospects. It demonstrates customizing D3 axes, including formatting tick labels with `d3.format`, adding grid lines via tick sizing, and appending custom axis labels. The chart uses `d3.scaleLinear` and `d3.scaleBand` for positioning, with data loaded from a CSV using `d3.csv`. Left axis ticks are removed to reduce clutter, and the x-axis tick format converts values to billions using an abbreviation.