Here are the Contacts app. You can see I'm running contacts. Here is the contact window. If I click on the red button, Contacts will actually close. The entire program ends. Why is there a difference in how some apps work when you click the red button and other apps? So there is a kind of logic that apps play when you decide what happens when you click the red button. It has to do with what I call single window apps. Whether an app actually consists of a single window or if there are multiple windows containing multiple documents used by the app.
So, for example, Contacts is a single window app. There is one window here that shows you your contacts, and you can click and click different, and it shows the contact on the right. It's a simple window. When you click on the red button, you close the individual window to end it. Other apps have multiple windows, usually because you can have multiple docks open.
For example, the easiest way to demonstrate this is on an app that undoubtedly shows you one window per document. Here are Pages, and we create a window that has this document in it. If I create a new document, it is in another window. I have two windows running now in pages. Now you can think that when you click the red button, you don't want Pages to quit because you have another document open. You can have three or four documents open. You certainly don't want the entire app to quit just because you've closed a window or document. So it follows that they should be consistent, and even when there is one window left when you close one window, the app remains open. After all, you can close the document to just go ahead and open another. So the app doesn't end. You must go to the menu and exit or use command Q to actually exit the app.
So we can look at other apps and see how they work. For example, Notes seems to be a simple window app. Sure enough if I click on the red button where Notes ends. Now if we go to something like TextEdit that has multiple windows. It's a document. There is another document. Of course, which one I close, it won't end the app. I close the last one and it doesn't close the app. I actually have to finish it myself.
Then there are apps that fall in between. Sometimes you can rationalize why they don't work this way. So you have iTunes. iTunes seems to be a simple window app. After all, there is no way for me to open a second main iTunes window. But if I click on the red button, it doesn't end. Well, this type makes sense because first of all there are two windows you can have. That you can switch between. So I could go to Window and open the iTunes window, or I can switch to MiniPlayer and bring it along. There is a second window, and if I close this first window, MiniPlayer remains open. If I close the MiniPlayer, it will automatically open the main window. So it's a little bit beyond a simple window app. Plus the fact that of course if I play music in iTunes and I want to close the window to get it out of the way, I don't want iTunes to quit because the music will stop playing. So it makes sense in that case.
However, there are some specific exceptions. In Calendar you have what looks like a single window app, but if you click on the red button, it doesn't end calendar. I can go to Window, Calendar. Now you can rationalize this a bit because there is something called the accessibility panel. You bring it and it's a kind of useful thing all in itself. Then the main calendar window closes to get the accessibility panel open, it makes a little sense. That might be why Calendar doesn't behave like a simple window app.
Of course, Safari is an app where you certainly often have more than one window open. So even though these are not technically documents, they are web pages, they are like documents. Then you close a window, close another window, you're still in Safari. It is very likely when you close a window in Safari that you may decide to open another one right away. You do not want to quit the app and have to go and restart it.
In some of these apps, like in Contacts, you're not going to say goodbye. I want to go see another contact. Let me close this window just to return to the same window. In fact, if you think about that rule, it makes sense. Therefore, Contacts ceases. There are also other programs. News is also the same. There is a single window for News. If I click to close it then the news ends because it would not make sense to close the news window just to open it again to go to another place.
So different apps do different things. For the most part, there is some logic behind it. It seems that in all cases when an app can handle multiple windows and multiple documents that click on the red button, the app will not end. It seems that in most cases when it appears that there is a window app that clicks on the red button, it will quit the app. There are a few exceptions, and these exceptions can be rationalizing a little to make sense. So I hope that explains it. It doesn't change much about how to use your Mac. But it is interesting to look at.