SAP GUI (Graphical User Interface) is a desktop application that provides users with a graphical interface to interact with SAP applications and systems. It serves as the primary interface for accessing various SAP transactions, reports, and functionalities. SAP GUI supports multiple platforms including Windows, macOS, and Linux, and offers different interface options such as classic SAP GUI, SAP GUI for HTML (web-based), and SAP Fiori Launchpad for a modern, role-based user experience. SAP GUI provides features like customizable layouts, navigation shortcuts, and integration with other desktop applications, enabling users to perform their tasks efficiently within the SAP environment.