WordPress themes are pre-designed templates that determine the look and layout of a WordPress website. They control elements like colors, fonts, and page structures, allowing users to create visually appealing sites without needing to code. Themes can be customized to fit individual needs, making them versatile for various types of websites, from blogs to e-commerce stores. There are thousands of WordPress themes available, both free and premium. Users can browse and install themes directly from the WordPress dashboard or purchase them from third-party marketplaces. Choosing the right theme is essential, as it impacts user experience and site functionality.