How to combine Two Images in Photoshop CS5.1

I just have seen this video to what exactly he has done in the last step? to combine two photos?

www.youtube.com/watch?v=ijST98XBcqg

Nothing at all. Very poor video. If you place photos be it on one or 3 layers and save it as a bitmap the saving process flattens the jpeg photos (any number of photos will do this) onto one layer therefore combining them. What the person was really showing was the difference that the filter achieved before and after and that was it.