Core Web Vitals, plainly
Three measurements, in ordinary language: how fast the main thing appears, how quickly the page responds, and how much it moves about.
Core Web Vitals get discussed as though they were arcane. They are three fairly intuitive questions about what a visitor experiences.
How fast does the main thing appear?
Largest Contentful Paint measures when the biggest element in view finishes rendering — usually a hero image or a headline. It is dominated by how quickly the server responds and how heavy that element is.
How quickly does it respond?
Interaction to Next Paint measures the delay between a tap and something visibly happening. Long-running JavaScript is the usual cause: the browser is busy and cannot get to the click.
How much does it move?
Cumulative Layout Shift measures content jumping after it has appeared. Images without dimensions, fonts swapping at different metrics, and banners injected above existing content are the classic causes.
This is the one users describe as the site feeling cheap, even when they cannot say why.
What to do with them
Use field data over lab scores, fix the largest offender rather than chasing a round number, and remember these are a floor. A fast page that does not answer the visitor's question is still a failure — just a quick one.