Use the Super key
When you press the Super key, you will be able to see your desktop. You can also press Super + S to see all of your open windows at the same time. This key can usually be found on the bottom-left of your keyboard, next to the Alt key, and usually has a Windows logo on it. It is sometimes called the Windows key or system key.
If you have an Apple keyboard, you will have a ⌘ (Command) key instead of the Windows key, while Google's keyboards have a magnifying glass instead.
To change which keys are used to display your open windows overview:
Type "Settings" into the global search bar on your desktop. Click on the resulting Settings icon, or press Enter, to open.
Click the Shortcuts tab.