A WordPress plugin is a piece of software that extends the functionality of WordPress. It adds new features or functionality to a WordPress website. There are thousands of WordPress plugins available, and they can be used to add a wide range of functionality to a website, such as contact forms, SEO tools, and e-commerce integrations. Plugins can be installed on a WordPress website from the Plugin Directory or by uploading a plugin file. Once a plugin is installed, it can be activated and configured from the WordPress administration dashboard.