This bar chart displays the population of various countries, sorted from largest to smallest for easy comparison. It is built using the Vega-Lite API, with the visualization specification defined declaratively in `viz.js` and rendered through the `vega` and `vega-lite` JavaScript libraries. The chart includes interactive tooltips provided by the `vega-tooltip` handler and is configured for full-window display, drawing data loaded from a CSV file using d3’s `csv` function, which fetches population data for 2015.