The example demonstrates two reusable legend components rendered in SVG: a color legend built with `d3.scaleOrdinal` mapping fruit names to categorical colors, and a size legend using `d3.scaleSqrt` for continuous numeric values with circular markers. Both legends are generated through custom functions that bind data to groups, with the color legend encoding categories via circle fill and the size legend varying circle radius. The code relies on D3 v5 selections, `.enter()`, and `.merge()` patterns to update the legends dynamically.