Isabelle M. answered 03/30/19
Patient and Versatile Apple and Video Production Trainer
Shift Command D is the shortcut when you are in Finder
You could also setup a Hot corner (System preferences>Desktop and Screen Saver>Screen Saver (at top)> Hot corner (button at bottom) Then you pick which corner you want to use and set its menu to Desktop. Then when you move your mouse to the corner of that screen, if will go to the desktop.
Command TAB also lets you quickly switch between open applications. The desktop is part of the finder