A constitution is the fundamental rulebook that organizes a state’s political and legal order. It sets out the basic principles guiding how power is exercised, describes the main institutions (such as the executive, legislature, and judiciary), defines their relationships, and establishes the rights and duties of citizens. It can be written (codified in one document) or unwritten (found in a mixture of laws, court decisions, and conventions), and it typically serves as the higher law that limits government action and governs how laws are made and applied. Key aspects to understand:

• Structure and powers: A constitution delineates who has authority, how that authority is exercised, and the boundaries within which government actors must operate.
• Fundamental rights: It typically protects core rights and liberties that cannot be easily overridden by ordinary legislation.
• Amendments and stability: Changing a constitution usually requires special procedures or supermajorities, reflecting its status as a foundational legal framework.
• Forms across countries: Some nations have written constitutions that are easy to read in a single document, while others rely on a collection of legal instruments and practices (uncodified or partly codified).

If you’d like, I can tailor this explanation to a specific country or discuss examples of different constitutional systems (for instance, how the United States, United Kingdom, and India approach constitutional law).