Mac OS, like most graphic user interface systems, uses the mouse as an input device. There are several basic mouse techniques you must know to use your computer:
Point to a specific item onscreen.
Click an item to select it.
Double-click an item to open it. an item to open it.
Press an item to activate it.
Drag to move an item or select multiple items.
Some computers use either a trackball or a trackpad instead of a mouse.