Introduction to the Mac user-interface. The Mac user interface is subtly different from the Microsoft Windows interface So we will spend a few minutes pointing out some of the differences. The Mac desktop. The Menu-bar and the Dock. A key difference: menu-bars.
saves an image of the entire screen to a file on disk
displays a cross-hair cursor which can be dragged over a smaller area if the screen required area (while the cross-hair is showing, a press of the space-bar brings up the further option to select a specific window for the image)