A Full Site Editing (FSE) theme, or a block theme, is a WordPress theme built entirely with blocks and designed to support the Site Editor. FSE themes enable users to visually create and customize all parts of their website, including headers, footers, sidebars, templates, and more, using the block editor. Unlike traditional themes requiring coding or specific theme settings to modify certain areas, FSE themes allow seamless customization across the entire site. With the Site Editor, users can edit the structure and layout of their site, change global styles such as color palettes and typography, and even create custom templates without writing any code. FSE themes typically include a theme.json file that defines the design framework, style presets, and overall settings, making creating and managing websites more intuitive and flexible for all users.