OPcache is a built-in PHP extension that dramatically improves your website's performance by storing precompiled script bytecode in shared memory. When a PHP script runs for the first time, it needs to be compiled into bytecode. Without OPcache, this compilation happens on every single request, wasting server resources and slowing down your site.

With OPcache enabled, the compiled bytecode is saved in memory. Subsequent requests for the same script execute the cached version directly, eliminating the compilation step. This results in:

• Faster page load times for your visitors.
• Reduced server CPU load, allowing your hosting to handle more traffic.
• Improved overall responsiveness of PHP applications like WordPress, Joomla, or custom code.

For most shared and cloud hosting environments, OPcache is enabled by default because the performance benefits are so significant. As a user, you typically don't need to configure it manually. However, if you're on a VPS or dedicated server, you might optimize its settings (like memory allocation) in the php.ini file for even better results.

In essence, OPcache is a transparent acceleration layer that makes your PHP-based website run smoother and more efficiently without any changes to your code. It's a critical component for modern PHP hosting performance.