PageSpeed Insights by Google is a tool that analyzes the performance of web pages on both desktop and mobile devices. It evaluates core web vitals like loading speed, interactivity, and visual stability, offering a score and specific recommendations to optimize website performance. Developers and website owners use this tool to identify and resolve performance issues, enhance user experience, and improve search engine rankings. PageSpeed Insights provides detailed diagnostics such as render-blocking resources, image optimization, and server response times, aiming to help websites run faster and more efficiently.