Core Web Vitals are Google criteria for evaluating the UX of a website. They include:
The LCP (Largest Contentful Paint) which measures the loading speed of the pages of the site;
The CLS (Cumulative Layout Shift) which checks the visual stability of a page;
The FID (First Input Delay) which measures the reaction of a page when a user presses a button.
Google realized that the FDI criterion was not very relevant. So he decided to replace it with the interaction with the following painting (INP), aperformance indicator (KPI) which measures the responsiveness of a page.