Finding information about a person, business or web site makes reverse lookup a popular tag. Reverse lookup refers to publications or web pages that allow you to obtain a name when all you may have is a telephone number or IP address.
For telephone numbers, reverse lookup works opposite a 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 reverse phone number directories are free while others charge fees, particularly those with databases for cell phone numbers.
An IP address (internet protocol address) is assigned to each device connected to the Internet. Because each one is unique, a reverse lookup can identify the domain name or web host name associated with an IP address. A reverse lookup of an IP address can be performed on any number of web sites.