The keyboard shortcut "Cmd + W" is commonly used on Mac computers to close the currently active window or tab. This command is particularly useful in applications like web browsers, text editors, and file management systems, allowing users to quickly tidy up their workspace without using the mouse. When you press "Cmd + W," the application will typically prompt you to save any unsaved changes before closing. This feature helps prevent accidental data loss, making it a convenient tool for managing multiple tasks efficiently while working on a Mac.