About actions

An action is a series of commands that you play back on a single file or a batch of files. For example, you can create an action that applies an Image Size command to change an image to a specific size in pixels, followed by an Unsharp Mask filter that resharpens the detail, and a Save command that saves the file in the desired format.
Most commands and tool operations are recordable in actions. Actions can include stops that let you perform tasks that cannot be recorded (for example, using a painting tool). Actions can also include modal controls that let you enter values in a dialog box while playing an action. Actions form the basis for droplets, which are small applications that automatically process all files that are dragged onto their icon.
Both Photoshop and ImageReady include a number of predefined actions, although Photoshop has significantly more user-recordable functionality than ImageReady. You can use these actions as is, customize them to meet your needs, or create new actions.