Site Speed
Site speed is the holistic measurement of how quickly a website loads, renders, and becomes interactive across a sample of its pages, as opposed to the speed of a single specific page. It is a confirmed ranking factor heavily influenced by the server infrastructure, Content Delivery Network (CDN) configuration, and the efficiency of the CMS codebase. A fast site speed is a prerequisite for passing Core Web Vitals. Slow site speed is an unacceptable technical failure that not only triggers algorithmic demotions but actively bleeds revenue by causing high-intent users to bounce before the page even loads.
Site Speed Simplified
Site speed is the overall measurement of how fast your entire website loads. If your site takes more than a few seconds to load, users will get frustrated and leave before reading anything. Google penalizes slow websites because they provide a terrible user experience.