A page builder is a Joomla extension or tool that allows you to create and design web pages visually without requiring extensive coding skills. It offers an easy-to-use interface with drag-and-drop functionality, pre-made elements, and customizable options. With a page builder, you can create complex page layouts, add content modules, customize the style, and arrange elements on the page the way you want. It simplifies the process of creating and customizing websites and offers flexibility and convenience.