The new Lightning connector on the iPhone 5 is sleek. It's smaller, thinner, and faster than the old 30-Pin connector that Apple has utilized for years. Even cooler is its ability to be inserted either direction as the port is reversible. There is one downside, however, and that is that your shiny new iPhone or iPod can no longer be used with old accessories.
That's why Apple has created an adapter that converts the old 30-Pin accessories to the new Lightning connector. Unfortunately, Apple missed shipping the new connectors out with the iPhone 5, but they appear to have now managed to get them out the door before the new iPods ship out.
The new adapter is pretty expensive, though this isn't unexpected as it is an Apple product. The cable itself has an authenticator chip which should keep third-party cables from being manufactured, and it wouldn't surprise me if this adapter featured something similar. Once someone gets one in-hand and tears it open, we will know if third-party ones will be able to be made.