Before you can research a company, you need a basic understanding of how companies are organized.
Companies are either publicly or privately held.
Most companies in the United States are private. Publicly held companies sell stock to the public and are required by law to provide certain information to shareholders and the government. Private companies are not legally required to disclose information about their operations and generally guard information about themselves very carefully. The result publicly held companies are easier to research than private companies. Financial information is filed under the name of the parent company.