Twitter on Monday officially unveiled its Promoted Accounts program and announced a "promoted products" option that will allow third-party apps to display promoted tweets and trends.

Promoted Accounts will add advertisers to Twitter's "Who to Follow" suggestions list.

"Promoted Accounts are suggested based on a user's public list of whom they follow," Twitter spokeswoman Carolyn Penner wrote in a blog post. "When an advertiser promotes an account, Twitter's algorithm looks at that account's followers and determines other accounts that those users tend to follow."

If, for example, a user follows many gaming-related accounts but does not follow Microsoft's Xbox feed, Twitter might suggest that that person follow @xbox. If there is no relevant recommendation, Twitter said it will not display a suggestion.

Promoted Accounts will start rolling out this week, but Twitter will only be testing it with a handful of companies, so not every user will see one. A Promoted Tweet will include a "promoted" banner underneath to identify it as an advertisement, just like Promoted Tweets.

Twitter will also allow outside apps to take part in its advertising program. Promoted Products for Partners is currently in a testing phase, with Hootsuite as the first partner.

"These partners will run Promoted Tweets in search and highlight Promoted Trends, sharing in Twitter's revenue for these products," Penner wrote.

Promoted Tweets, meanwhile, are being bumped from the bottom of the trending topics list to the top "because we've been pleased with the quality of Promoted Trends and people are finding them useful," Penner said.

Twitter is currently working with over 40 advertisers, the company said, and the "new Twitter" allows other opportunities for those companies to add pictures and video to their ads.

The news comes on the same day that Evan Williams stepped down as Twitter's chief executive and named chief operating officer Dick Costolo as the company's new CEO.