Persistent object cache is a caching mechanism used to store PHP objects in memory or in faster storage such as Redis or Memcached.
In the context of WordPress, persistent object cache can improve website performance by storing database query results and frequently called PHP objects, thus reducing server load and page loading time.

When WordPress runs, PHP objects are generated every time the page loads.
These objects include pages, widgets, posts, and more.
In most cases, these objects are generated from database queries and time-consuming processes.
With persistent object cache, the results of database queries and frequently called PHP objects are stored in the cache so that they do not need to be re-generated each time they are requested.

In WordPress, persistent object cache can be enabled using plugins like Redis or Memcached.
Once activated, these plugins will store PHP objects in memory or faster storage and can be accessed again when the object is needed.
By using persistent object cache, WordPress websites can become faster and more responsive as it reduces server load and speeds up page loading time.