The internal governance document of a corporation that sets rules for how the board and shareholders operate.
Bylaws are the internal rules that govern how a corporation runs. They cover the mechanics of governance: how and when board meetings are held, how directors are elected, what constitutes a quorum, how shareholder meetings work, how officers are appointed, and similar procedural matters.
Think of Articles of Incorporation as the birth certificate of a corporation (it's the public filing that creates the entity) and Bylaws as the rulebook (the private document that says how decisions get made). Bylaws are adopted by the initial board of directors at the organizational meeting shortly after incorporation.
For early-stage startups, bylaws are often standard documents prepared by formation services like Stripe Atlas or Clerky. They don't need to be complicated. What matters is that they exist, are properly adopted, and that the company actually follows them — because failing to follow your own bylaws is one factor courts look at when deciding whether to pierce the corporate veil.