System-wide notifications were a highlight feature for Windows Store apps in Windows 8, and Windows 10's new Action Center lets you actually manage them, making notifications useful rather than one-off shouts into the wind.
You might not want every Windows Store app you install barking at you all the time, or maybe you don't want to see any notifications while you're in presentation mode. To change your notification settings, go to 'Start menu->Settings->Systems->Notifications and actions'. Individual Store apps tend to have more granular notification options in the Settings menus inside the apps themselves.
