Web components rendered on the server, loaded on the client only when needed. The platform does the work, the framework just says when.
This component's data function ran on the server to fetch the current
time. Its code is set to loading: 'eager', so the
client-side JavaScript loads immediately after the page streams in.
This component was rendered on the server, but its code is set to
loading: 'visible'. No JavaScript was loaded for it until
it scrolled into the viewport.
Open the network tab, scroll to the top, refresh, and scroll back down to watch the chunk load on demand.