The example demonstrates interactive filtering of categorical data cards, where each card is colored according to its group (A, B, or C) and labeled with the group name. A dropdown menu lets users select a group to display, showing only matching cards and removing others with a gray fade-out transition. The visualization uses D3 v4’s data join, `transition`, and `selection.exit().remove()` to handle dynamic updates, with a static dataset of 24 objects. Filtering is driven by a `change` event listener on the select element, and card styling relies on inline HTML and CSS classes.