WordPress Plugin
A package of code that adds or extends functionality in WordPress without modifying core files. Plugins use WordPress hooks to integrate cleanly.
A WordPress plugin is a piece of software that adds specific features or functionality to a WordPress website. Plugins are installed separately from the core WordPress software and interact with it through a system of hooks (actions and filters).
There are over 60,000 free plugins in the official WordPress.org repository, plus thousands of premium plugins sold through third-party marketplaces. When an existing plugin does not meet your needs precisely, a custom plugin can be built to match your exact requirements.