This tutorial is dedicated to Photoshop novices as it is very basic tutorial where you will learn how to record your first action and how to use it. Actions can speed up your work and save your time because with using them you can automate routine editing of your pictures.
Shortly about actions:
An action is a series of tasks that you play back on a single file or a batch of files—menu commands, panel options, tool actions, and so on. For example, you can create an action that changes the size of an image, applies an effect to the image, and then saves the file in the desired format.
Actions can include steps 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.
In Photoshop, actions are the basis for droplets, which are small applications that automatically process all files that are dragged onto their icon.
Photoshop come with predefined actions installed that help you perform common tasks. You can use these actions as is, customize them to meet your needs, or create new actions. Actions are stored in sets to help you organize them.
You can record, edit, customize, and batch-process actions, and you can manage groups of actions by working with action sets.(Source: http://helpx.adobe.com/photoshop/using/actions-actions-panel.html)
How to import downloaded Actions:
Actions are saved on the hard drive as .ATN files. If you are donwloading actions you can save them as the ATN file to the default Actions folder - default path is on C:\Program Files\Adobe\Photoshop CS”\Presets\Actions on PCs. Then open Photoshop and click on the arrow in the upper-right corner of the Actions bar. Select the “Load” option from the menu that appears, and find your ATN file. This causes the action set to appear in your Action list.
You can browse, find, download and use different Photoshop actions HERE
How to record and use Actions
For better imagination check this tutorial: