This example shows a small social network of eight named individuals organized into four groups, with weighted links connecting them. The visualization uses a force-directed layout to position nodes and links in an SVG. It is built with D3 v4, employing the `d3.layout.force` API to simulate physics, and renders circles and text labels for nodes, with lines for edges. The data comes from `data.json`, and the code explicitly sets gravity, charge, and distance parameters to control the layout. Link stroke widths and node fills are styled via CSS, though the stroke width does not actually reflect the link weight.