Page speed plugin is a type of software or tool that can be added to a website or content management system (CMS) to improve the loading speed and performance of web pages. These plugins typically use various optimization techniques such as minifying code, compressing images, and caching to speed up the loading of pages. Some popular examples of page speed plugins include W3 Total Cache, WP Fastest Cache, and Autoptimize. These plugins are mostly used in WordPress websites, but some are also available for other platforms.