The "Cmd" key, also known as the "Command" key, is a modifier key found on Apple keyboards. It is used to perform various shortcuts and commands in macOS, enhancing user efficiency. For example, pressing Cmd + C copies selected text, while Cmd + V pastes it. In addition to basic functions, the Cmd key is integral to many applications, allowing users to quickly access features like saving files or opening new windows. It plays a similar role to the Ctrl key on Windows keyboards, streamlining tasks and improving workflow for users across different software.