POD is relatively new. It's part of the digital age of publishing -- a book is printed when a consumer wants it. The book is digitally stored and a copy is printed when it is ordered from the publisher.
I've heard derisive comments such as, "Oh, that book is a POD." Oh, well!!!
For the uninformed, many publishers, and not only the small operations, use POD technology. While the print-per-book is higher, it sure saves the publisher on having unsold books returned to its warehouse by bookstores. Sometimes it does benefit the consumer when they purchase books on the remainder tables. But the bookstore doesn't profit much, the publisher profits little (if any) and the author doesn't see a dime for his efforts.
POD has helped e-book publishers offer their titles in trade or hardback copies -- one at a time. And it has helped keep publishers afloat by not having to have large print runs, keep books stored in warehouses, and deal with returns (for the most part).
As for self-published books, they've been around for many years, long before POD. And by the same token, POD has been a blessing for them because they haven't been forced to order a "minimum" of books. Just check out Amazon, B&N and other e-book/POD opportunities.
I've had books published the traditional way and POD. There's really not a difference. A book is a book is a book.
So just remember, when you order a book from a POD publisher, it's still a book. Just one at a time!