Natural-born citizen
A natural-born citizen is someone who is born in a country and is given citizenship status because of his native birth, as opposed to immigrants who become citizens by applying for citizenship. In the United States, citizenship is automatically conferred on those who are born within its jurisdiction.
Natural-born citizenship is listed in the United States Constitution a requirement of the President, as found in Article II section I: "No person except a natural born Citizen, or a Citizen of the United States, at the time of the Adoption of this Constitution, shall be eligible to the Office of President...."
There has been some controversy as to whether President-elect Barack Obama is a natural-born citzen because he has not revealed his birth certificate.