Finding information about a person or business when all you have is their telephone number makes reverse phone directory a popular tag. It refers to publications or web pages that allow you to obtain a name or address based solely on a telephone number.
As the name suggests, a reverse phone directory works opposite a standard telephone directory. Traditionally, you use a telephone directory when you know the name and want the phone number. With a reverse directory, you can look up the the identity of the person or business with the telephone number. Some sites allow access to a reverse phone directory for free while others charge fees, particularly those with for cell phone numbers.