1 WHAT'S GOING PUBLIC?

Alibaba operates dozens of businesses-sharing traits with the likes of eBay Inc., Amazon.com Inc. and Google Inc. The sprawl has led to some confusion among U.S. investors, said Victor Anthony, an Internet media analyst at Topeka Capital Markets. 'Investors are uncertain exactly what assets will be included as part of the IPO,' he said.

Among its units, Alibaba's Taobao site offers a consumer-to-consumer marketplace. Brands like Nike and Disney use its Tmall site as a marketplace to sell directly to Chinese consumers. Alibaba also has a 'cloud-computing' business that, like Amazon's Web Services unit, lets companies rent computer storage and processing power over the Web rather than buying their own servers. One thing that won't be included in the deal, according to analysts and Wall Street Journal reporting, is the Alibaba-affiliated PayPal-like company Alipay.

2 WHAT'S THE REVENUE BREAKDOWN?

While Alibaba's recent overall revenue figures are known, it's unclear exactly what parts of the company are driving that growth. The IPO filing is expected to show which business lines are most important, which are picking up steam and which are slowing.

3 HOW MUCH MONEY GETS SPENT THROUGH ALIBABA?

Alibaba is largely a middleman, helping sellers market their wares and buyers find what they need. And for the most part, it makes money by charging commissions on those sales. That makes transaction volumes one of the more important metrics points for investors looking to understand both Alibaba and the growth of China's online retail market in general.

The Wall Street Journal has reported that Alibaba's Taobao and Tmall sites reached $240 billion in combined transaction volume last year. By way of contrast, EBay posted $76.5 billion last year in so-called 'gross merchandise volume' excluding vehicles.

4 HOW MUCH CASH DOES THE COMPANY HAVE?Alibaba has spent more than $3.5 billion since the start of last year on acquisitions, The Wall Street Journal has reported. Investors will want to know if it can continue its buying spree, and if so, what types of companies is it looking to acquire? IPO filings typically contain a balance sheet and cash-flow statement which detail how much cash the company is generating, and how much it has in the bank. Investors will also likely have questions about what the company plans to do with its cash. But investors may not get all the info they want on this front, as IPO documents are typically light on management predictions about future deal making.

5 WHAT WE WON'T KNOW:For starters, how big the IPO actually will be. The top of the filing will include a proposed dollar value of the size of the IPO, but this number is just a placeholder used to calculate certain fees and is almost sure to change. The company will disclose its estimated valuation in an amended F-1 filing when it launches its marketing 'road show' months later. Knowing Alibaba's proposed valuation is crucial to investors, who will compare valuation metrics like its price-to-earnings ratio with those of already-public peers. The first filing will also lack details on how many shares the company or existing holders are offering, and may not detail first-quarter financial results.