A professional corporation (PC) is a corporation of professionals. In some states, some professionals are permitted to form corporations under specific regulations, to allow the professionals to have the benefit of a corporation while meeting ethical requirements. In a corporation, the shareholders and officers are free from personal liability, but this would be a problem for a corporation formed by professionals, if they formed the corporation in order to absolve themselves of responsibility for their professional actions (malpractice). The PC form does not allow professionals to be free from personal liability from the result of his or her professional actions, but it does allow other shareholders or directors to be protected from the actions of another.
PC's function in much the same way as a limited liability partnership (LLP), but under the rules of incorporation rather than partnership. The ability to form a PC is determined by individual states, and states determine which professionals may form professional corporations in their state.