Reverse phone lookup is a service wherein a person can identify a caller by entering the phone number into a search engine to look up the person or business that owns it. The service is offered free of charge by most online search directories, including Whitepages and Yellowpages.
Reverse phone lookup requires a 10-digit number and can be used to obtain the address, neighboring contacts and a map with directions to the location. The free service does not provide ownership information for numbers that are unlisted or that belong to a cell phone. However, many directories offer advanced services that provide that, as well as other background details, for a fee.