Why there are two buttons in a mouse?

One button, the primary, is used to click on objects in order to select, open, or manipulate them. The other button, the secondary, is used to call up a menu of available operations of choices relating to the object clicked, so as not to automatically summon the object's default action (usually Open).
One button, the primary, is used to click on objects in order to select, open, or manipulate them. The other button, the secondary, is used to call up a menu of available operations of choices relating to the object clicked, so as not to automatically summon the object's default action (usually Open).