One major difference between Macintoshes and Windows or Linux computers is how applications behave.
In both Windows and linux, everything is oriented to the windows of a program. If you close all of the windows or the main window, the program quits. This is not the case on a Macintosh. You can have a program running on a Macintosh with no windows open. The "correct" way to completely get rid of a program on a Macintosh is to select "Quit" from the application menu. If you simply close the window, the program will remain running.
The same concept goes for hiding programs. You can minimize windows on a Macintosh, but it is better to select "Hide" from the application menu because then the program's windows don't take up any more space in the Dock.