A constitution is a set of fundamental principles, established precedents and legal procedures that a country follows in its governance. A Constitution is said to be a Written Constitution when these principles are written down into a single document or set of legal documents.
The British Constitution is the only unwritten constitution in the world whereas the rest of the world have Written Constitutions. Most of the constitutions are Codified Constitutions. A constitution is said to be a Codified Constitution when the principles, precedents and legal procedures are written down into a single comprehensive document.
Constitution is usually a product of necessity due to unavoidable call for freedom and rights and is known for its role in limiting the state power by establishing constitutional lines which the rulers cannot cross.
The Indian Constitution is the longest written constitution in the world with 448 articles, 12 schedules and 100 amendments in its constitution whereas the US Constitution is the shortest with only seven articles and 27 amendments.