Term Kind Topic What it is
Hydration concept Hydration Cost The browser attaching interactivity to server-rendered HTML by re-running component logic, during which the page looks ready and is not.
Islands Architecture Partial Hydration, Selective Interactivity, Component Islands pattern Hydration Cost Rendering a page as static HTML with independently-hydrated interactive regions, so JavaScript is shipped and executed only for the parts that need it rather than for the whole page.
Partial Hydration Islands Architecture, Selective Hydration pattern Hydration Cost Attaching client-side interactivity only to the components that need it, rather than reconstructing the whole page's component tree in the browser.
Time to Interactive Gap metric Hydration Cost The interval between a page appearing complete and actually responding to input, during which the user's taps do nothing.