Largest Contentful Paint should be under 2.5 seconds, Interaction to Next Paint under 200 milliseconds, and Cumulative Layout Shift under 0.1. They are measured from real users' browsers, not a lab, and they are a ranking signal.
They are also the honest test of a build. A site can look finished and fail all three because images are unsized, scripts block the thread and fonts swap late. Our CWV Drift Monitor extension watches them as you browse, and our builds target 100 on all three.
Real user data appears in Search Console's Core Web Vitals report about a month after a site has enough traffic, and it is that data, not a lab score, that Google ranks on.