The example demonstrates two reusable legend components rendered as SVG: a color legend mapping fruit names to ordinal colors, and a size legend using a square-root scale with circular marks. Both legends are built with D3 v5, using `scaleOrdinal`, `scaleSqrt`, data joins with `selection.enter()`, and merge operations to update tick groups. The color legend draws lines labeled with fruit names, while the size legend displays circles sized by the scale with tick text offset by radius. Styling is applied via CSS classes for tick text and circle strokes.