Corporations are generally private arrangements authorized by the State. They are governed by a combination of statutory and common law. In short, the Corporation enjoys a certain legal status, including certain rights and privileges, and in exchange the corporation submits to a legal framework governing aspects of the internal and external activities of the corporation.
To take advantage of this framework, the person or people representing the corporation (incorporators) have to specifically take advantage of the legal framework. This is done by creating Articles of Incorporation, and then filing them with the Secretary of State to give the State notice of the arrangement. By filing Articles, the person or people for the corporation are representing that there is a legally legitimate and binding arrangement being put in place that complies with the statutory framework and constitutes a corporation.