Yep. But you can also make your own in PS. It's practically a saved sequence of editing steps. For example: You first reduce the saturation, then increase the contrast, then add a drop shadow. You can save these steps into an action called #1. Now when you have the next photo, you don't have to do all the steps individually, but just run the action.
There are a lot of actions available on the internet, that combine editing steps to make your photos look better or apply a certain visual style to them. But you can also use actions for pretty much anything you do regulary in PS. For example I have an action to create the photo "holes" in some of my png quickpages. My action adds a white frame to the photo layer and then cuts out the background under the photo. So you see, it's just a time saving method.
Also the big advantage is, that you dont have to re-invent the wheel every time, when someone has already found a wonderful way to edit a photo. You download their action, apply it to your photo and voila! The disadvantage is, that not every photo is the same. So you sometimes have to tweak a bit to make it fit your particular picture.
