The AMP plugin provides a PHP-port of the AMP Optimizer as a library providing automated server-side optimizations of AMP pages, including a variety of performance best practices for AMP. These optimizations improve key performance metrics such as the very important Last Contentful Paint (LCP) performance metric when AMP pages are served from origin.
In essence, the AMP optimizer implementation corresponds to a Transformation Engine (TE), which receives a regular (i.e. unoptimized) AMP page, and applies a serial pipeline of Transformers (i.e. optimizations). The TE then outputs an optimized AMP page, ready to be served to users and meet the desired CWV thresholds.
To learn more about AMP optimizers, what they do, and why they are key to maximize the performance of your AMP pages, check this documentation in the AMP’s project site.