An SVG visualization demonstrates enter, update, and exit states for circle elements using D3’s selection API. It begins with six circles drawn horizontally, initially colored black based on a `scaleOrdinal` mapping. The code shows how newly created data objects receive attributes through chained `.data().enter()`, while subsequent selection updates fill colors, and `.exit().remove()` deletes elements. The example relies on D3 v7’s declarative selection methods with explicit data-driven updates.