Core Web Vitals measure how a page feels to actual visitors. Largest Contentful Paint tracks how quickly the main content appears, Interaction to Next Paint tracks how quickly the page responds to clicks and taps, and Cumulative Layout Shift tracks how much content jumps around while loading.
These metrics are part of Google's page experience signals and, more importantly, they correlate with whether visitors stay. Common improvements include smaller images, less third-party script, reserved space for media, and serving pages from a CDN.