This example shows a grouped bar chart comparing values across three categories for multiple groups, with each category represented by a colored bar. The visualization uses D3.js v4 to load data from a remote CSV file, which is parsed with `d3.csv`. Bars are rendered as SVG rectangles, with an ordinal color scale mapping categories to red, blue, and green. The X-axis uses `d3.scaleBand` for group positioning, while a nested subgroup scale positions bars within each group, and a linear scale maps values to the Y-axis.