Google now allows domain owners to suggest keywords for their “AdSense for Domains” to Google, about the types of content users are looking for when they arrive on an undeveloped domain. “They’re used to help our system determine the best ads to place on these domains. For eg., www.rockstarsand.com, publisher might suggest keywords "bitumen" and "mining" so that ads may appear from advertisers offering oil extraction products. Keyword hints remain optional. When keyword hints are provided by publisher, our ad-matching systems will use them more often. As always, we aim to provide the most relevant ads for user, the best value for advertisers, and the best returns for publishers. This means in some cases, keyword hints will be ignored when we’ve evidence that other targeting approaches perform better,” explained AdSense blog.
More info: AdSense for Domains Quick Start Guide