Simple definition
A WordPress plugin adds features to a site without directly modifying WordPress core files.
Technical definition
Plugins use hooks (actions and filters) and may register settings, custom post types, REST endpoints or scheduled tasks. Updates and third-party dependencies can affect security and compatibility.
What is it used for?
Add functionality, such as a contact form or caching, while keeping themes and core independently maintainable.
Practical example
For example, install a form plugin, configure SMTP delivery, then test submissions and check the plugin for updates.
Common issues
- Plugin or theme conflict
- Incompatible update
- Cache hiding the change