Move over Facebook, Alibaba's mega IPO is coming

The tech company behind the largest and most-anticipated IPO of the year doesn't trace its roots to Silicon Valley, a Harvard dorm room or MIT lab.

Alibaba was founded 15 years ago in the modest Hangzhou, China apartment of Jack Ma -- a former English teacher who started the company with an initial investment of $60,000 kicked in by 18 friends.

The company has since evolved into the dominant force in China's e-commerce industry, a market with so much potential that Alibaba's IPO may be the largest ever by a tech company -- surpassing even the $16 billion raised by Facebook.

Alibaba is often described as a combination of Amazon(AMZN, Fortune 500) and eBay (EBAY, Fortune 500), with some PayPal sprinkled in to boot. 

By one estimate, almost four out of every five dollars spent online in China are spent in Alibaba's marketplaces.

On last year's Singles Day -- China's version of Cyber Monday -- sales on Alibaba's shopping sites clocked in at $5.7 billion, more than double America's Cyber Monday figure.

The company's top two e-commerce sites, Taobao and Tmall, attract more than 100 million unique visitors each day, on par with what Twitter (TWTR) reported before its IPO.

Unlike Amazon, the company does not sell directly to consumers. Instead, it allows users to search the merchandise offered by sellers in thousands of digital stores.

The website design is distinctly Chinese. Each page is crammed with products in an effort to mimic a crowded Chinese market. Buyers and sellers often use a built-in messaging service to chat with each other, and haggling over prices is standard.

Alibaba is more than its flagship marketplaces. It also runs a wholesale operation, a cloud computing business, and Alipay -- a digital payment service. In a first step into finance, the company has started to offer investment funds.

The scale of the business is massive -- and profitable.

Yahoo has a 24% stake in Alibaba, and its financial reports offer a peak at the company's earnings. Alibaba's sales rose 66% in the fourth quarter of 2013 versus the year prior, while earnings surged 110% to $1.4 billion. In the most recent quarter, Facebook (FB, Fortune 500) reported income of $523 million and Amazon earned $177 million. Twitter has yet to post a profit.