In macOS and OS X it’s possible to show one application at a time. You can enable a ‘single application’ mode by entering the following command in Terminal:
defaults write com.apple.dock single-app -bool true;killall Dock
When you click on an application in the Dock you’ll only see the windows of that application. All other windows are hidden in the background. You’ll be able to focus more on that one application without being distracted by any other applications in the background.
To revert to the original settings:
defaults write com.apple.dock single-app -bool no;killall Dock