There: that was it.  Any questions?  hehe.  The sky is selected with the magic wand tool in this case.  You can right click and select inverse to capture the mountain range as a selection.

To take it further: Selections...you cannot produce graphic design without them essentially.  A selection is something that you can create from one layer or image to produce a localized effect (image adjustment, filter..) on a portion of the layer.  However, more often you will create a 'selection' for the purpose of making it another layer where you can then do further changes to it and modify it as it's own independent layer. 

You make selections essentially to isolate a certain part of an original image to make changes to it.  You will make selections a lot in graphic design when you want to "cut out" a person (horse, cigar, car, etc.) and put them onto another document for part of a design.  Here I am dragging a 'selection' (of the girl) onto another image with the move tool.

For example, say you have a family picture with a straggler at the edge of the photo but you want to move them closer to the rest of the family, you would create a selection around that person, put them onto their own layer (layer via cut or copy).  Once a selection you have created is on it's own layer, you can move it around with the move tool (V) as it has now become independent.  Now you can move the straggler closer to the rest of the family.  You can now use options such as copy and paste or the clone stamp tool to repair the area that is left behind.

Here's another example to help you better understand what a selection is.  Let's say that you have a picture of a building but you want just that building onto another document so you can put a gradient background behind it.  What you would do is make a 'selection' of the building (using any of many different methods taught in the Basic Photoshop DVD Training) and then you would drag the building selection with the move tool onto another document (you could also Copy: File: New: Edit: Paste).  Now you have the building separated from the rest of the original image because you "made a selection" and in this case you moved it to another document.  Now you can create a sunset gradient or whatever you want to do on the underlying background layer (you may have to create a new layer to do this).

You can also apply filters or image adjustment to "selected" areas on a layer while leaving the "unselected" area of the layer untouched.  Be careful when doing this if you don't make a copy of the original layer or you could be stuck with it (without a snapshot of history).  Remember that you create selections to 'isolate' a desired part of the image (layer) that you want to be independent.  Once it is 'independent' you can do an assortment of things but most importantly as a graphic designer, you can put it into a deliberate design of your own vision.  You can have many layers of 'selections' that you have carefully made and you can harmonize them into a beautiful graphic design.

There are dozens of ways to get a perfect selection (depending on the situation) and is perhaps the longest time consuming method for even professional Photoshop users to master because it varies with each new image and the possibilities for error are greater with more complicated selections.  The new extract tool works really well for complicated selections, but with patience and dedication you can become quite well at making selections without too much effort. 

Now you should understand what a selection is and how vital it is to graphic design.  Now you can focus on getting perfect selections. The art of the Selection is an advanced and ongoing study which I will continue to cover throughout your free Photoshop Design education.  If you are interested in covering most of the methods to make a selection you can check out the Photoshop Designer training package and there will also be free tutorials available for you throughout the PSDer Experience.

- Article by Orion Williams copyright 2004