Twitter will unveil on Tuesday 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.

Several companies will run ads, including Best Buy, Virgin America, Starbucks and Bravo.

“The idea behind Promoted Tweets is that we want to enhance the communications that companies are already having with customers on Twitter,” said Dick Costolo, Twitter’s chief operating officer.

Since Twitter started in 2007, its growth has resembled a hockey stick, increasing almost in a vertical line. According to comScore, Twitter.com had 22.3 million unique visitors in March, up from 524,000 a year ago, and that does not include the millions more who use the service through third-party smartphone and Web applications like TweetDeck or Tweetie.