Computerworld - https://www.computerworld.com/article/3023544/apple-mac/24-keyboard-shortcuts-mac-users-need-to-know.html#tk.rss_all
I’m sure most Mac users know Command-C means copy and Command-V means paste, but there’s a host of other useful shortcuts that make a Mac user’s life much easier. I’ve assembled this short collection to illustrate this truth:
Closes the active window you are currently in. Use Option-Command-W to close all currently active app windows.
[ Further reading: 40 tips to get the most from your Mac (and macOS ‘High Sierra’) ]