Advertising has begun invading social media and most of the popular social media services have already started to include ads in their mobile apps. Facebook has hopped onto the bandwagon and it seems Twitter is following suit with its Promoted Tweets now appearing on its mobile apps.
Functioning like ordinary tweets, Promoted tweets are tweets purchased by advertisers and can be retweeted and replied to. Previously not found on mobile devices, Twitter has announced that Promoted Tweets will now appear on iOS, Android and other mobile platforms. The tweets will appear in the timelines of iOS and Android Twitter apps, and will only appear once. The tweet stays in your timeline, though users can choose to dismiss it from the timeline.
Source: Twitter Advertising Blog