The U.S., or the United States of America, is a federal republic composed of 50 states, a federal district, and several territories. It is known for its legal system, which is founded on the Constitution and includes a system of checks and balances among the three branches of government: legislative, executive, and judicial. Understanding the U.S. legal framework is essential when looking at legal citation as it forms the basis for how laws and cases are referenced in various legal documents.