Public companies sell shares of the company (stocks) to the general public, and are required to submit financial information and annual reports to the U.S. Securities and Exchange Commission. Public companies are therefore easier to research as a general rule of thumb.
Subsidiaries of public companies can be difficult to research because the parent company is not required to report on each of them individually. Therefore, when researching a subsidiary, you often have to read carefully through reports about the parent and look for references to the subsidiary.
We're not researching Private companies for this assignment but it is good to know the definition.
Private companies do not sell publicly traded stocks and as a result, are not required to release as much information to the government or the general public They are therefore more challenging to research.