A choropleth world map visualizes population per country, with a deeper red fill indicating a higher population using a sequential red color scale in a [minimum, maximum] population domain. It plots country paths and a graticule using the d3.geoNaturalEarth1 projection and d3.geoPath API. The code joins population data from world_population.csv, reading the '2022Population' column, to the topojson feature collection of world countries, and fetches the atlas via topojson-client.