Final answer:
The National Provider Identifier (NPI) is a unique ten-digit alphanumeric assigned to healthcare providers for identification in billing and record-keeping.
Step-by-step explanation:
The National Provider Identifier (NPI) is a unique ten-digit alphanumeric identifier that is assigned to healthcare providers in the United States by the Centers for Medicare and Medicaid Services (CMS). The NPI is used for a variety of purposes, including billing, record keeping, and in various healthcare databases to identify providers in a standardized manner. Unlike a patient's name, social security number, or date of birth, the NPI is specifically designed for healthcare providers and is not related to personal identification information of patients.