Unlike Windows, just clicking the X (red button) in an app window doesn’t close the app. It stays running in the background, and open in the Dock until you manually quit by right clicking and selecting Quit, or using the Command + Q keyboard shortcut.
Unfortunately, Google’s Chrome browser doesn’t respond to this shortcut, requiring the user to hold both keys instead. It’s worth noting, however, that this delay is by design since the Command + W (close a single tab) shortcut is close to the Command + Q (quit app) command. This, of course, will lead to the occasional accident where you close the app entirely instead of just a tab. It’s not the worst thing in the world, and stops some accidental closures, but having one app behave differently from everything else can get a little annoying.
For those irritated by the delay, it really couldn’t be simpler to change. Google, thankfully, added a menu item to remove the warning and the delay.
1) Open Chrome from the Dock.
2) Click Chrome to open the menu.
3) In the menu that opens, uncheck Warn Before Quitting.