Chapter 1 - Purpose and Background
All applicants who meet the eligibility requirements to derive or acquire citizenship or to become naturalized  United States citizens are eligible to receive a certificate from USCIS documenting their U.S. citizenship.  The burden of proof is on the applicant to establish that he or she has met all of the pertinent eligibility requirements for issuance of a certificate.
The Certificate of Citizenship is an official record that the applicant has acquired citizenship at the time of birth or derived citizenship after birth. 
The Certificate of Naturalization is the official record that the applicant is a naturalized U.S. citizen. 
USCIS strictly guards the physical security of the certificates to minimize the unlawful distribution and fraudulent use of certificates.
In general, in order to obtain either a Certificate of Citizenship or a Certificate of Naturalization from USCIS, a person must:
File the appropriate form and supporting evidence;
Appear for an interview before an officer, if required;
Meet the pertinent eligibility requirements, as evidenced by USCIS approval of the form; and
Take the Oath of Allegiance, if required.
USCIS District Directors, Field Office Directors, and other USCIS officers acting on their behalf, have delegated authority to administer the Oath of Allegiance in USCIS administrative oath ceremonies and to issue certificates. 
[^ 1] The Immigration and Nationality Act (INA) defines naturalization as the “conferring of nationality of a state upon a person after birth, by any means whatsoever.” See INA 101(a)(23). Accordingly, any person who obtains citizenship after birth, even if that citizenship is obtained by automatic operation of law, such as under INA 320, is a “naturalized” citizen under the law. For ease of reference, this volume uses the term naturalized citizen to refer to those persons who do not acquire automatically but instead file an Application for Naturalization (Form N-400) and proceed through the naturalization process in their own right.
[^ 2] A person who automatically acquires citizenship may also apply for a U.S. Passport with the Department of State to serve as evidence of his or her U.S. citizenship.
[^ 4] See the relevant Volume 12 [12 USCIS-PM] part for the specific eligibility requirements pertaining to the particular naturalization provision, to include Part D, General Naturalization Requirements [12 USCIS-PM D]; Part G, Spouses of U.S. Citizens [12 USCIS-PM G]; and Part I, Military Members and their Families [12 USCIS-PM I].