A Tree Map visualization displays a hierarchical dataset of names using an expandable and collapsible tree diagram. The code uses D3.js version 3.5.17 with the `d3.layout.tree` for layout and `d3.svg.diagonal` for drawing curved links between nodes. Nodes are rendered as purple circles with labels, and clicking a node toggles its children to show or hide them. The visualization animates with 750ms transitions, updating node positions and link paths smoothly as the tree structure changes.