This section is primarily about sources for finding out what a company does, what it makes, what services it provides, how companies are organized, what is their strategy, etc.. Also, while this section's primary focus is on doing current research, a lot of sources have a long publishing history and can be used for those looking to research the past.
There are a few basic steps to start with when researching public companies. Since they are required to submit financial statements to the Securities & Exchange Commission (SEC), all sorts of information is widely available.
The Investor Relations area will have financial filings, conference call records/transcripts, press releases, SEC filings, etc. They may not keep financial filings there forever (see the WayBack Machine External or databases if they aren't available) but this is often where you can find out about the officers and directors, the corporate history, and other things the company feels it is import to tell investors.
However, the rest of the company web page can also tell you important things about them--how they see themselves, how they organize by business line, how they organize geographically, who their clients are, people/companies they do business with, projects they are undertaking, etc. Of course, some companies will be more forthcoming than others, and each will be organized according to the needs of its company and with its own idiosyncrasies.
The next place to look are in filings the company has to make with the proper regulators. In the United States, that is mainly the Securities & Exchange Commission (SEC), though energy companies and banking companies have additional oversight. The SEC instituted the electronic filing system in 1994, so filings for U.S. companies are there beginning in 1994 (and a bit earlier in a few cases). There are a number of subscription sources for SEC filings but searching and downloading is free on the SEC web site. The advantages for some of the subscription-based services are more advanced free text searching and the ease of formatting/downloading of the reports.
There are a number of filings the SEC requires but there are a few that are going to be the most helpful to those looking for what the company does.
For those who are looking for fuzzier or more nebulous, information like marketing, strategy, competitive perspective, R&D, intellectual property, etc., there are a few suggested sources of information though what is included can vary company to company. For example, those doing research on retail companies may be looking for company locations, number of stores, square feet managed, etc. while those doing research on pharmaceuticals may be interested in R&D/intellectual property figures. Some of this can be found in SEC filings though full-text databases can also be helpful. In SEC filings, this type of information can be found most often in different sections including:
Here are a few specific things and where they can be found in a 10K:
Below are Subscription resources that are good for doing research on public companies. These are sources that have company information that is more data focused though there may be some news/articles. However, for a more complete list of databases that have arcticles from news and industry sources see the sources listed under the Searching the News section of this guide.
The subscription resources marked with a padlock 
are available to researchers on-site at the Library of Congress. If you are unable to visit the Library, you may be able to access these resources through your local public or academic library.
Also included are the Ford Equity Research Reports (aka: Mergent Equity Investment Research Reports) - Mergent Online offers the current issues of multi-page equity research reports released weekly for over 5500 U.S. companies. The reports provide ratings, recommendations, sector analysis, and company financial information. For the previous 3 years of this title please see the Mergent Archives database.
