Google asked:

Ad management allows you to store details about an AdSense unit, including ad size, colors, and channel settings, on our servers. Using this feature, you don’t need to update the code on your page to update your ads. Instead, you can make changes to the AdSense units on your pages from within your account. For more information please visit – http://www.google.com/adsense/support/bin/answer.py?answer=69807