Literally a public company is a company owned by the public. There are two uses of this term.
A company that is owned by stockholders who are members of the general public and traded publicly. Ownership is open to anyone that has the money and inclination to buy shares in the company. It is differentiated from privately held companies where the shares are held by a small group of individuals often members of one or a small group of families or otherwise related individuals (or other companies). For a discussion of the British and Irish variant of this type of company, see public limited company.
A government-owned corporation. This meaning of a "public company" comes from the fact that government debt is sometimes referred to as "public debt" (however there are no "public bonds"), government finance is sometimes called "public finance", and so on.
