1) To "maximize" the size of any window, click on the Maximize button or double-click anywhere along the colored title bar at the very top of the window. (The title bar usually has the program name and the name of the file that you have open, if any.)

2) To "minimize" the size of any window down to a gray, rectangular button at the bottom of the screen (i.e., on the "Taskbar"), click on the Minimize button.   To bring the window back up to where it was on the screen, just click on its button on the Taskbar.

3) To "restore" the size of any window to about halfway between maximum (or full-screen) and minimum (i.e., a button on the Taskbar), click on the Restore button (the one that replaces the Maximize button when you click on the Maximize button).