The visualization compares the environmental impact of different protein sources, showing that mealworms require the least land, feed, water, and warming compared to cattle, pork, and poultry. It uses a grid of small orange rectangles, where each rectangle represents one unit of feed, and the number of rectangles grows based on the feed value from the data.csv file. The code relies on D3 v4 APIs such as `d3.select`, `d3.csv`, and `g.append` to parse the data and position the rect elements in an SVG canvas.