I had told you in one of my last articles about the relationship between webpage and brochure and the transition we made from brochureware to permissionware. Your webpage as being seen like a flyer or a page of a brochure that has the goal of delivering useful information wrapped into a digital experience that makes the information easily and smartly consumable should be designed to raise the user experience level. Your webpages should be compliant with the user's demands and devices set. This goes as far as how this page is loaded, how fast it is, and how pictures are rendered. Core Web vitals is a set of metrics that allow search engines like google to rate the page experience of your website along with Mobile-friendliness, safe-browsing, HTTPs, and no intrusive interstitials. If we take the case of Google, this search engine starts separating mobile ranking and desktop ranking by using only the data of a mobile website to compute the ranking score for searches coming from mobile devices. The same is done for desktop. This separation of mobile and desktop rankings and search results is induced by the fact that the experience in both of those devices is different and how we design and publish, and layer content on each of these devices are different.
with the Chrome User Experience(CrUx), Google CrUx gives you all the data your website’s core web vitals score and some guidance of the ways you have to score high.
You can get more information on page experience by reading this