A public corporation is a business whose securities are traded on the public stock exchanges. A private company is held solely by its owners and is not traded publicly.
A big difference between private and public companies involves public disclosure. A public U.S. company trades on a stock exchange and must file quarterly earnings reports with the SEC that are accessible to shareholders and the public. Private companies do not trade on an exchange. They are not required to disclose their financial information or file disclosure statements with the SEC.

Public companies have the advantage of raising capital by selling stock or issuing bonds. Private companies don’t have that luxury. When they need capital, private companies turn to private funding, which can boost the cost of capital or limit expansion.

Some companies want to stay private. For example, United Parcel Service keep private from its founding in 1907 until it went public in 1999. While the majority of the first shareholders probably didn’t fully recognize the value of their shares, they found out when the stock started trading on a public exchange and its price was determined by public demand.