On a Mac, you can use the "Force Quit Applications" feature to close an application or task that is not responding. To access this feature, you can press the "Command" and "Option" keys on your keyboard, then hold them down and press the "Escape" key. This will bring up the "Force Quit Applications" window, which displays a list of all open applications. You can select the application or task you want to close and click the "Force Quit" button to close it.
Alternatively, you can use the "Activity Monitor" application to view and manage running tasks on your Mac. To access this application, you can press the "Command" and "Space" keys on your keyboard to open the spotlight search, then type "Activity Monitor" and press "Enter" to launch the application. The "Activity Monitor" application allows you to view detailed information about each task, including its CPU and memory usage, and provides options to quit or force quit tasks as needed.