A face built with D3.js is rendered as a yellow circle with black outline, featuring two eyes and a curved mouth, all contained in an SVG. The example demonstrates a simple animation where the eyebrows move up and down via a transition loop. The code uses D3's `select`, `append`, and `arc` APIs to construct the facial components, with the mouth created using an arc path with specified radii and angles. The entire composition is centered dynamically in the viewport.