A choropleth map shows the total number of airline passengers traveling to and from India for 54 countries, using a cyan-to-red color scale to represent traveler counts. The visualization loads flight data from a CSV file via `d3.csv`, then passes it through JavaScript to a Google Charts GeoChart, which renders the geographic regions. The code also references D3 v4 and a TopoJSON file for US states, though the map itself is drawn by the Google visualization API.