Short Answer:
A constitution is a statement of the basic principles and laws of a nation, state, or group, such as the U.S. Constitution. Another very common meaning of constitution is the physical makeup of a person. ... If you have a strong constitution, it means you don't get sick very often.
Long Answer:
The Constitution of the United States established America’s national government and fundamental laws, and guaranteed certain basic rights for its citizens.
It was signed on September 17, 1787, by delegates to the Constitutional Convention in Philadelphia. Under America’s first governing document, the Articles of Confederation, the national government was weak and states operated like independent countries. At the 1787 convention, delegates devised a plan for a stronger federal government with three branches—executive, legislative and judicial—along with a system of checks and balances to ensure no single branch would have too much power.
We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defense, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America."
The Bill of Rights were 10 amendments guaranteeing basic individual protections, such as freedom of speech and religion, that became part of the Constitution in 1791. To date, there are 27 constitutional amendments.
America’s first constitution, the Articles of Confederation, was ratified in 1781, a time when the nation was a loose confederation of states, each operating like independent countries. The national government was comprised of a single legislature, the Congress of the Confederation; there was no president or judicial branch.
The Articles of Confederation gave Congress the power to govern foreign affairs, conduct war and regulate currency; however, in reality these powers were sharply limited because Congress had no authority to enforce its requests to the states for money or troops.