Ownership of public companies is divided into shares of stock that are listed on a stock exchange or an over-the-counter market.
Public companies must meet reporting standards, which increases the amount of available information on the company.
Private companies are not listed on a stock exchange. They can have shares but these are not publicly listed. There are varying amounts of information available for private companies.
Hint: Search online with the company name and "annual report". For example:
NAB "annual report"
Australian or international ranking of companies with shared characteristics, e.g.
top 10 telecommunications companies by revenue.
Analysis of the Strengths, Weaknesses, Opportunities and Threats of a company.