Field data vs lab data
Also called: Lab data, Real user monitoring, CrUX
Field data is measured from real users; lab data comes from a controlled test like Lighthouse.
Definition
Lab data is repeatable and great for debugging; field data shows what real users experience. They often disagree, and both are useful in a bug report.
In practice
Lighthouse looks fine on your laptop, but field data shows LCP of 4 s for most mobile users.