What does hidden windows mean?

Mission control supposed to show everything running on Mac. The definition for Mission Control given by this website also confirms that (see the screen shot shown bellow. EDIT: This has now been corrected after this question).

But, I cannot see the hidden windows in my Mission Control. What am I missing?

EDIT: Apple support page says Mission Control is the quick way to see everything that's currently open on your Mac. Does this mean hidden windows are closed? What does actually hidden windows mean?

Solution 1:

Mission Control is the quick way to see everything that's currently open on your Mac.

The above statement from the Apple help page WAS true, but now it is OUTDATED. Mission Control used to show all open windows including hidden ones, but Apple excluded hidden windows from the list in the recent versions of OS X. But the documentation is not updated yet.

(About your 2nd question: Hidden windows are not closed windows, they are open ones, but you cannot see them until you make them unhidden. Please note hidden windows are shown in app expose)

Solution 2:

You shouldn't take a tag description on a web site not affiliated with Apple as a feature description. See http://support.apple.com/en-us/HT204100 for how Apple defines Mission Control (emphasis mine):

Mission Control is the quick way to see everything that's currently open on your Mac. To use Mission Control, do one of the following:

• Swipe up with three or four fingers on your Trackpad
• Double-tap the surface of your Magic Mouse with two fingers
• Click the Mission Control icon in the Dock or Launchpad
• On an Apple keyboard, press the Mission Control key

In Mission Control, all of your open windows and spaces are visible, grouped by app.