In the United States, public companies sell shares in the company to the public on a stock exchange. In the United States, regulators at the Securities and Exchange Commission (SEC) require companies to file annual and quarterly financial reports and disclose how much they pay their executives, who is on the board of directors, and the known risks of investing in the company. Private companies do not sell shares in the company to the public though they may have private investors. They don't have to disclose financial information, salaries, profits, losses, or any management information. For these reasons, researching private companies can prove challenging.
Search the company's website for information. Check the "About Us," "Contact," and "Investor" pages for SEC Filings and other information.