Final answer:
A specific identifier in an address that represents an entity is called a Uniform Resource Locator (URL). If an online source has a Digital Object Identifier (DOI), it should be used for citations instead of a URL.
Step-by-step explanation:
If a specific identifier in an address represents an individual, agency, corporation, school, etc., it is known as a Uniform Resource Locator (URL). A URL is the address of a resource on the Internet and is used to retrieve web pages and files online. When citing online sources, if your source has a Digital Object Identifier (DOI), you should use that instead of the URL. A DOI is a permanent identifier provided to electronic documents, making them easily findable even if the URL changes over time.