What does Lighthouse’s ‘Eliminate render-blocking resources’ warning mean?

This warning means the browser has to download and process certain CSS and JavaScript files before it can show anything on screen - so those files are holding up your whole page from appearing:

• Render-blocking CSS - the browser will not paint until it has the stylesheets it needs, so a big or slow stylesheet stalls everything.
• Render-blocking JavaScript - scripts in the page head pause rendering until they finish loading and running.
• The fix is to defer or split - load only the critical styles up front, and add defer or async to scripts that do not need to run immediately.

This is usually a job for whoever built your site or your theme’s performance settings, but it is one of the highest-impact fixes because it directly improves first paint and LCP. Ask your developer to defer non-critical CSS and JavaScript - it is a known, well-documented fix.