Graphical User Interface" and is pronounced "gooey".  It refers to the graphics on the screen that allows users to click, drag and drop with a mouse instead of using the command prompt.  Learn more here.

A display that also serves as an input device that can be used with a special pen device or fingers

The software that communicates with the hardware and allows other programs to run.  (such as Windows XP, Windows 7, Apple OS X)

A board made of keys which, along with a mouse, serves as a primary input device for a computer. 

The horizontal strip that contains lists of available menus for a certain program.