WordPress plugins are apps that allow you to add new features and functionality to your WordPress website, similar to the way mobile apps do for your smartphone. There is a popular saying in the WordPress community, ‘There’s a plugin for that.’
WordPress is designed so that other developers can add their own code to it. The WordPress plugin API offers a robust set of hooks and filters which allow developers to modify existing WordPress functionality or add new functionality.
You will find your plugins on the Plugins » Add New page in the admin sidebar. Here you can activate and deactivate your existing plugins and install new ones.