Twitter formally announced its plans to go public on Tuesday, saying it will sell shares under the ticker symbol TWTR. Here’s what you need to know about the Twitter IPO before the social networking site goes public.

Growth

Though Twitter is still not profitable, the social networking site is growing fast. In 2012, Twitter's sales rose 198 percent to $316.9 million compared to the year before. In the same period, the company's net loss decreased by 38 percent to $79.4 million.

However, Twitter’s losses seem to be growing even as the company's revenue is rising. In the first half of 2013, Twitter reported revenue of $253.6, pointing toward a much better year than 2012. However, losses also shot up sharply to $69 million in the same time frame, up from $49 million in the first half of 2011.

As for the growth of Twitter’s userbase, the company is heavily American at the moment, but hopes to increase its numbers in other countries soon.

"In general, a higher proportion of Internet users in the United States uses Twitter than Internet users in other countries," Twitter said in its registration statement. "Accordingly, in the future we expect our user growth rate in certain international markets, such as Argentina, France, Japan, Russia, Saudi Arabia and South Africa, to continue to be higher than our user growth rate in the United States. However, we expect to face challenges in entering some markets, such as China, where access to Twitter is blocked, as well as certain other countries that have intermittently restricted access to Twitter."

Revenue Per User

One of the best ways to measure performance for a social networking company is the amount of revenue per user. Currently, Facebook brings in roughly $2.17 per user, while the more business-oriented LinkedIn reports sales of $1.93 per user. But Twitter prefers to report a completely unrelated metric.

Instead of reporting revenue per user, Twitter tracks ad revenue by timeline views. According to Twitter’s IPO, its advertising revenue per 1,000 timeline views is $2.17 in the United States and $0.30 outside of America. Twitter defines such timeline views as “the total number of timelines requested when registered users visit Twitter, refresh a timeline or view search results while logged in on our website, mobile website or desktop or mobile applications (excluding our TweetDeck and Mac clients, as we do not fully track this data).”

Revenue Stream

Twitter's revenue comes almost solely from advertising. While Twitter also monetizes its data stream, selling data trends to marketers and TV networks (hence Twitter’s purchase of Trendr and Bluiefin Labs), this income is still small in comparison to its advertising revenue. For instance, about 84 percent, or $269 million, of Twitter's 2012 revenue came from advertising. Only $50 million came from data servicing.

This year, ad revenues have shot up to $221 million in the first six months alone, more than doubling ad revenues from the first six months of last year. At the same time, data services have increased 53 percent to $32 million. While Twitter’s ad revenue is growing, the company acknowledges that it must keep increasing its ad sales even further to become profitable.

Facebook

The big elephant in the room is how the Twitter IPO will compare to Facebook’s bumpy launch in 2012. Though Facebook had the single biggest IPO for a tech company, it soon lost half its value, partly due to its growing base of mobile users. Most investors are hoping that Twitter can overcome such a bump.

One big difference between Facebook and Twitter is the way that users log on to the service; specifically, Twitter is a much more mobile-centric network. Twitter says that about 60 percent of its active users log on to Twitter via a mobile device. For most social networks, this would be a problem, as it’s generally harder to display advertising on crowded mobile layout. Twitter, however, says that it already gets more than half of its revenue from ads on mobile devices, far more than Facebook, Bloomberg reports.

See Twitter’s complete IPO filing below.

Twitter S-1 filing

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