Indeed. You don't
need a Safari window open to still use Safari, as it may be downloading something in the background. You don't
need a Mail window open to still use Mail, as it is constantly checking for incoming messages.
If an application can function without an open window or can spawn multiple windows, then it can run without being "open".
Again, for instance, you don't need an open Text Edit window to create a new Text Edit document! You simply go to File>New. That operation does not require a window, simply a menu function, and thus will remain "running" while not "open".
Imagine if you had to start Text Edit all over again just because you saved and closed that last window. I hated juggling stuff like that in Windows. It's not necessary. I remember having to keep in my mind to leave at least
one Word document open so I wouldn't have to start the program all over again to open another document, hahahaha. Oh primitive Microsoft. You don't even have virtual desktops yet XD
Finally: iPhoto is not capable of having more than one window open at any time. iPhoto is reliant on a single window. Thus, closing that window quits the application, as no functions can be performed without that window open
