Core Web Vitals
Google's three measures of how a page feels to real visitors: LCP for loading, INP for responsiveness, CLS for stability.
The thresholds are 2.5 seconds, 200 milliseconds, and 0.1, and a site passes only if all three are met. They are read at the 75th percentile of actual visits, which is the part people miss: a page that is fast on a desk machine and slow on a three-year-old phone fails, because the slow quarter is exactly what the percentile keeps.
That is also why a lab score and a field score disagree so often. The lab tool measures one load under conditions you chose; the field data measures your visitors, on their devices and their networks, over 28 days — and only the second one counts here.
The set is not fixed forever. Measures have been replaced before, most recently when INP took over from First Input Delay, so a dashboard built around a metric name deserves a check now and then.