Core Web Vitals are three measures of how a page feels to load and use, from the point of view of a real person. Google reports them from real Chrome users and treats them as a light ranking signal, but the reason to care is the reader.
Largest Contentful Paint is how long until the main content appears. Aim for under two and a half seconds. It is hurt by a slow server, heavy pages and render blocking scripts and stylesheets in the head.
Cumulative Layout Shift is how much the page jumps around as it loads. Aim for under 0.1. It is caused by images and embeds with no set dimensions, and by content injected above what you are reading.
Interaction to Next Paint is how quickly the page responds when you tap or click. Aim for under 200 milliseconds. Heavy JavaScript is the usual cause.
Kenovar measures the basics at the edge, response time, page weight and what blocks first paint, and pulls the real-user figures from Google when a key is set. Set width and height on images, cut render blocking resources and keep the page light.