This visualization shows yearly sales performance, combining bar charts for total sales in millions of dollars with a line chart for total units sold. The code uses d3.rollup to aggregate the raw CSV data by year, then d3.scaleBand and two d3.scaleLinear instances create dual axes. SVG rendering displays the bars and line, with axes, labels, and a legend using d3.axisBottom, d3.axisLeft, d3.axisRight, and d3.join.