In order to form a corporation (S or C corporation), the first legal document you must file with your state’s secretary of state (or other state agency) is called the Articles of Incorporation (also called a Certificate of Incorporation, or Incorporation Certificate in some states). You must file the Articles of Incorporation with your appropriate state agency because state laws are responsible for incorporation filings, not federal laws. That is why you can create a corporation in any state. It is also why there are different rules in every state for corporations (but many of the rules are very similar from state to state).
The Articles of Incorporation represent the single legal document that "gives life" to the corporation. Without the Articles of Incorporation there can be no corporation. However, you’ll also need an incorporator(s), i.e. the person who sets up the corporation, and you’ll have to properly complete and file the Articles before a state will recognize your corporation.
While the Articles of Incorporation serve as the "birth certificate" for the corporation, it also functions to create a contract between the corporation and its shareholders, a contract between the corporation and the state, and it puts the general public on notice about its existence.
Next, let’s take a look at where the articles of incorporation fit into the grand scheme of setting up a new corporation.