Constitutional law is an area of law that shows how the institutions of a country are organised, and the basic rights rights of citizens. In most countries, such as the United States, this is found in a written text called a constitution. Some countries use a lot of different texts and unwritten rules instead, such as the United Kingdom.
Constitutional law explains how different institutions relate to each other. For example, the relationship between the legislature, executive, and judiciary. In a federal country, constitutional law explains what the powers of the central government and state governments are.