Applications remain in dock after closing

As explained, some apps quit when clicking the red close button, many do not. No, there's no way to control it other than always using command Q or quit from the apps main menu, avoiding the red close button entirely.

EnricaPelv wrote:

Thanks, so the only way to make an application disappear from the dock is to click Quit? How come then some applications disappear from the dock when you click the red x, and others don't? Is there any way to control that?

Apps that have no reason to exist when the last document window is closed will quit (System Settings). Apps that can do something (like open a new document or check for new email) without any windows will not quit. There is no way to control it. Just use Quit if that is what you want to happen when you click the close button. If you just want to close the document you are working on, use the close button (or command).

The red X doesn't close everything. For instance, click the red X for Firefox and the app essentially moves to minimized. It's still running as noted by the tiny gray dot under the icon on the Dock.

Note the tiny gray dot:

To close FF you have to click Firefox then Quit Firefox