On a Mac computer, when you open an application the window will have three buttons on the upper left-hand corner of the window. The Red button is to Exit the window/app, the Yellow button is to Minimize the window/app, and the Green button is the Maximize to Full Screen mode. Once you click on the Green button, the window will be in Full Screen mode, so you must move your cursor all the way to the top of the screen in order to view the three buttons again because they are hidden in Full Screen mode.
For that reason, I prefer not to use the Full Screen mode and instead I just double-click the title bar of the opened window which maximizes it without entering Full Screen mode, so the menu and Title Bar of the window would still be visible. [NOTE: If double-clicking the Title Bar of the open window doesn't work, you will have to enable that option it in the System Preferences (Grey Gear) under the Dock section.]
