The shell is the interface that allows users to communicate with the operating system. In macOS, this comes in two main forms: • **Command-Line Shell:** Accessible through the Terminal application, where the default shell is Zsh (Z Shell). This text-based interface lets users execute commands, run scripts, and perform system tasks directly. • **Graphical Shell:** Known as Aqua, it is the visual interface of macOS. Aqua provides the familiar elements like windows, icons, menus, and the Dock, making it easy for users to interact with the system without needing to use command-line commands. • **Role:** Whether through a text interface or a graphical one, the shell translates user inputs into commands that the operating system (and ultimately the kernel) can execute.