This example shows a horizontal bar chart of population data for 20 countries in 2010, with each bar labeled by country name and sized by population value. The visualization uses React to render SVG elements, with D3’s `scaleBand` and `scaleLinear` for positioning, and `format` to abbreviate axis tick labels (converting "G" to "B" for billions). Data loads from a remote CSV file via `d3.csv` in a custom `useData` hook. The code also defines reusable axis and mark components, and includes tooltips on each bar using SVG `<title>` elements.