There’s no such thing as Publish-On-Demand, even though horrid PublishAmerica insists that “Publish-On-Demand” is the real meaning of “POD.” (Most of the world knows that it means “Print-On-Demand.”)
“Publish-On-Demand” makes no sense, but companies want you to think they’ll provide it.
Llumina Press, BookSurge, Outskirts Press and others have advertised the meaningless phrase aimed at ignorant writers who may think that "publishing" is more exciting than "printing," or don’t know the difference between the words. They’re not the same thing! Printing is part of publishing (except for e-books). Printing can be done on demand. Publishing can’t be done on demand.
Publishing is a complex, multi-stage process which takes a writer’s words from manuscript to books being sold. The end result of a publishing project—which may be a million books or just one book—can take weeks, months or even years.
With Print-On-Demand, books are printed one at a time or a few at a time, as orders are placed by readers through booksellers. Books are usually in the hands of readers a few days after an order is placed. That could not happen if a publishing company had to start the entire publishing sequence each time that an order for a book arrives.