A theme and a plugin are two different components of a WordPress website. A theme is a set of visual designs and functionality that makes up the overall look and feel of a website. It includes the overall design elements like layout, colors, sidebars, typography, and more. A plugin, on the other hand, is a piece of software used to extend the functionality of a website. Plugins are developed by third-party developers and are used to add specific features and capabilities to a website, such as contact forms, search functions, ecommerce, and more. Themes provide the design and coding structure of the website, while plugins provide the specific functionalities that can be added to the site. A WordPress website typically has both a theme and a plugin installed for it to work properly.