A naturalization application allows lawful permanent residents (green card holders) to apply for U.S. citizenship after meeting specific residency and eligibility requirements. Applicants must generally have lived in the U.S. for at least 5 years (or 3 years if married to a U.S. citizen), demonstrate good moral character, and pass English and civics tests. Successful applicants become U.S. citizens, gaining full rights, including voting and applying for a U.S. passport.