A choropleth map colors countries according to the number of students per country, with a sequential red color scale and a legend showing count ranges. The visualization uses D3 v5’s `d3.geoMercator` projection and `d3.geoPath` to render world topology from the World Atlas TopoJSON, while data from a TSV file is joined to country features. Country boundaries are styled with white strokes, and hovering highlights the selected country.