What is digital compositing?

Digital compositing is creating a new image by assembling various disparate pictures into an organic-looking whole. I use stock images from dreamstime.com, my own photos, vintage photos from Ebay, items scanned into the computer, etc. Photoshop is my base program for manipulating the images, but there's a world of choices beyond (or rather in addition to) PS. Photoshop is my one true love : D

On my website I post simple composites in large files for people to download and print for free, as a way to practice my art and build a following (katemcwethy.com). Here is an example of 3 stock photos:

The end result of compositing (which typically is 8 hours' worth of work) is this:

Book illustrations use a lot more "parts" - a dozen or more, depending on the complexity of what I'm trying to create. Edgar Allan Poe is quite a challenge in that respect.