Short version: CMS stands for content management system: software used to create, edit, organize, and publish website content.
A CMS lets editors manage pages, posts, media, menus, categories, and structured content without rewriting code for every change. It usually separates content management from the public design, so the team can update information while templates, themes, or components control how that information appears on the website.
WordPress is one common CMS example, but the same idea appears in many platforms. A good CMS setup gives the business enough flexibility to publish quickly while still protecting consistency. For larger sites, structured fields, reusable templates, permissions, and content types become important because they keep editing practical as the website grows.
Related terms: WordPress, custom post type, and ACF.