The state filing document that officially creates a corporation.
Articles of Incorporation (sometimes called a Certificate of Incorporation) is the document filed with the Secretary of State to create a corporation. For a Delaware C-Corp, you file with the Delaware Division of Corporations. The document typically specifies the company name, registered agent, number of authorized shares, and par value.
Unlike Articles of Organization for an LLC, the Articles of Incorporation for a corporation often include provisions about stock: how many shares of common and preferred stock the company is authorized to issue. These numbers matter because they set the ceiling on how many shares can exist.
After the Articles are filed, the corporation exists legally but isn't fully set up. You still need to adopt bylaws, hold an organizational board meeting, issue founder shares, adopt a stock option plan, and have founders sign PIIA agreements.