When Twitter started, the founders said that they would not include advertising in the service. To make money, the company said they would attempt to sell corporate accounts "of some sort." They've slightly adjusted that plan when they launched their promoted tweet service. Now they are adding to their advertising services with a new plan to advertise deals and events under the handle @earlybird.
The promoted tweets show at the top of your search results on Twitter wether you follow the company or not. The new Earlybird service works a little differently, all of the tweets will show up in your timeline along with the other users you follow on Twitter. If you don't follow @earlybird you won't see the tweets. According to the Twitter Help Center, "Twitter @earlybird Exclusive Offers are special time-bound deals, sneak-peeks, and events that are promoted by the official Twitter @earlybird account. We partner with select advertisers and retweet offers that they have crafted only for the Twitter community." At launch @earlybird plans to advertise deals from retailers along with sneak peaks and events. Twitter also has plans to post local deals similar to those offered by Groupon. The deals will initially be targeted at users based in the U.S., with plans to add international deals in the future.
Beyond the deals Twitter has already made with partners, they are asking that its users submit events and companies they think Twitter should work with.