Print on Demand Publishing
Print on demand is precisely what it purports to be. Printing is only undertaken when an order is received for the publication; in other words, when there is a demand. In many respects, it is, or can be, a form of self publishing, if undertaken by the writer.
Many publishers (sometimes called small presses) specialise in PoD and the method has been greatly facilitated in recent years by advances in digital publishing, allowing very short print runs or even individual books to be produced.
It is, however, common for PoD produced books to be more expensive for the reader to buy, as the economies of scale of the large commercial printer cannot be achieved. For the retailer, though, this needs to be offset against the advantages of not requiring to hold or warehouse stock, which can be expensive, especially when thousands of books are involved across a wide catalogue.
Like self publishing, there is an excellent Wikipedia entry on print on demand which is well worth reading.
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