Largest Contentful Paint (LCP) measures how fast the main content appears. Cumulative Layout Shift (CLS) tracks visual stability—unexpected jumps annoy users and hurt forms. Interaction readiness matters for menus, accordions, and calculators.
You do not need to become an engineer. Ask for a baseline report, a target (“good” thresholds), and a plan when you add new scripts or third-party widgets—those are common sources of regression.
Good hosting, image sizing, and careful use of animations usually move the needle more than micro-tweaking fonts.
