Public companies are required to disclose certain information in order to issue stock and be traded on a stock exchange. Also investment analysts write reports about companies, their operations, products & services. Information on public companies is generally easy to find and widely available. A company's website and its annual report give information from the company's perspective whereas analysts are external to the company and generally more critically objective.
Private companies can be large like Dell which makes it easy to find information about them. They are a major competitor in their product lines with other large players. If a private company is small, newly founded or closely held, finding public information may be difficult. You should begin with the company databases, then take second steps to look at news articles about the company. If more information is needed, sometimes learning about the background of the principals in the business is the most productive path to information.
Hoovers - Best first choice; has the most listings for both public and private companies. Open the PARENT company report and scan the contents on the left side: Company Summary, SWOT, Competitors, Strategic Initiatives, Significant Developments, Analyst reports.
Business Insights: Essentials - competitor to OneSource; sometimes not as up-to-date; has Investment Reports (another name for Analyst reports) form other sources and Market Share for many companies.
MarketLine - contains major public and private companies; must use the COMPANY option in the RIGHT SIDE pull down box.
Special Note: Many of the SWOT reports in Hoovers come from MarketLine however if they don't give MarketLine as the author then they are written by Hoover's analysts. SWOTs from different sources gives you more than one independent opinion about a company.
PrivCo - primary reports on private companies and investment funding; yet large companies are listed showing what lines of business they are acquiring.
News and articles give business news and background information about a company. The Business Journals (website) has weekly business newspapers from major cities and covers local/small companies as well as large. No need to login; simply search in the upper right hand corner for the company name.
The following are library databases:
Proquest Business Searching this database is similar to using Business Source Complete; some overlap in articles but enough unique ones to make it worthwhile.