Facebook's IPO filing with the SEC is about 170 pages long and contains tons of details on its advertising business.

Eighty-three percent of Facebook's $3.7 billion in revenues come from advertisers, and the social network spends another half billion a year promoting itself.

It is one of America's largest advertisers, and largest ad sales businesses, at the same time.

We've boiled all that down to 12 crucial facts, numbers, charts and trends.

From CEO Mark Zuckerberg's personal opinion on the role of his advertisers to the company's fear of bad PR, here's everything you need to know about Facebook's ad business.

Facebook Makes $1 Billion Per Quarter—Just From Ad Sales

Facebook made $943 million in advertising revenue in Q4 2012. That puts Facebook on course to sell well over $1 billion in ads in Q1 2012.

Facebook is itself a big advertiser.

Facebook spent $427 million on marketing and sales in 2011, up from $184 million the year before. That growth rate suggests its sales and marketing will easily blow past the half a billion dollars mark in 2012.

In 2011 it saw a 46 percent increase in the number of employees in global sales, business development, and customer service. (The company didn't give actual numbers.)

Facebook's annual ad business: $3.2 billion and growing.

Ad revenue in 2011 was $3.2 billion, up 69 percent from $1.9 billion in 2010. There was also a 42 percent increase in ads delivered in 2011. The difference between the percentage increases occurred because there was an 18 percent increase in the price of ads 2011.

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See Also:

• Facebook Claims It Increased P&G's Deodorant Sales By 9%
• Google’s New Privacy Policy: What’s the Big Deal?
• Facebook Says Growth Of Mobile Users Threatens Its Ad Revenue