Actions act on objects, and are a basic part of working with them. For example, printing the contents of an object uses the Print action. Starting an application for a data file object uses an Open action, or some other application action.
The Selected menu contains a list of commands followed by a list of actions you can use with the selected icon. The contents of the actions portion of the Selected menu change depending on the type of icon that is currently selected.
The action listed at the top of the action portion of the menu (the default action) is the action that will be taken when you double-click a file or folder. In the menu shown in the figure, the default action is Open In Place.
The default action is the first action listed in the actions portion of the Selected menu.