Actions aren't as complicated as they might seem. All they are is a set of commands or actions that you can record or run'. If you go to the actions palette you can see that there are different default action sets that you can load (production, image effects, etc.).
When you open these folders you have option of choosing an action
to run.
To run an action select it in the actions palette and then press the
triangle run' button in the middle bottom of the palette. If you
choose molten lead' for example it will run through all the steps
involved (previously recorded') to create a molten lead effect. You
can view the results in the layers palette. Usually running a
default action will create more snapshots in the history palette.
You can choose many different Actions to run after
you've loaded the folders from the palette menu. Try loading and
then running some of these.
If you open an effect folder you can see the detailed commands of
the actions which makeup everything that is run' within Photoshop
to complete that action.
Note how it creates this effect automatically (when you try it)? All you have to do is run' the action by pressing play' on the actions palette.
It's put a layer above the layer you were on using Screen blending mode.
In this image you can see that I've made some custom adjustment layers. These are very powerful. I cover them in-depth in the Basic Photoshop DVD Training program including tons of other educational tutorials.
If you want to make a new document with the same image dimensions, just select the background layer. Select All.
Edit: Copy and then File: New and then Edit: Paste to put the other background image onto this one.
The easiest way to do this is just Image: Duplicate (if you only have a few layers) and then drag other layers to the trash. It's good to know many ways of doing things; Photoshop is filled with these. There are often many ways to come up with the same results. It's up to you to figure out what's best to do for you in each case once you have the level of understanding.
More Photoshop: 
