The term "Windows UI" refers to the user interface of the Windows operating system, which is developed by Microsoft. It includes elements like the Start Menu, taskbar, and desktop icons, allowing users to interact with their computer easily. The design focuses on usability, providing a familiar layout for navigation and access to applications. Windows UI also incorporates features like File Explorer for managing files and folders, and Settings for system configuration. Over the years, it has evolved to include modern design elements, such as flat icons and responsive layouts, enhancing the overall user experience across various devices.