POD is printing on demand. It is a concept that has been around for many years. I remember when I first saw it demonstrated, it was a big machine that spit out a bound softcover book. It was thought at first that the machine would replace book stores with printing kiosks in malls. I thought it was a very exciting idea. All of the books in the world could be digitized and the called up on demand and printed out.
At the same time, ebook devices were taking that same digital content and special dedicated reading devices were available like the Rocket eBook and Softbook. While the Palm, the PDA at the time could also show ebooks, it was a little hard to read on such a small screen.
So it all shook out, the ebook devices morphed into tablets. The POD machine never made it to the mall, and the mall started to wane anyway. Amazon was perfectly positioned to launch Createspace to fill the demand for vanity publishing fulfilled through their online store Amazon.com.
We are glad they did and have enjoyed making books and magazines over the years at a very reasonable cost.