The New York Times reports that Twitter will today unveil a much-anticipated plan for making money from advertising, finally answering the question of how the company expects to turn its exponential growth into revenue. The advertising program, which Twitter calls Promoted Tweets, will show up when Twitter users search for keywords that the advertisers have bought to link to their ads. Later, Twitter plans to show promoted posts in the stream of Twitter posts, based on how relevant they might be to a particular user.