This bar chart visualizes population by country for 2015, with bars sorted in descending order and tooltips displaying exact population values on hover. The visualization is built using the Vega-Lite API, which programmatically constructs a Vega-Lite specification through methods like `markBar()` and `encode()`. Data is loaded asynchronously via `d3.csv` from a Gist hosted CSV file, and the chart renders to SVG using Vega. Custom styling is applied through a configuration object to adjust axis labels, ticks, and tooltip appearance.