A virtual phone number is a telephone number is used to route calls to the user's actual phone number or numbers. Virtual phone numbers are often used to enable long distance service without incurring long distance charges in IP telephony and for call forwarding services, such as find me / follow me.
A virtual phone number makes it possible for someone within a specified area code call an IP telephony user in another area code as if it were a local call. Here's how it works: A VoIP (voice over IP) customer asks their service provider to assign them a virtual phone number within a desired area code. When someone in that area code dials the virtual phone number, the call registers as if it were local, but seamlessly maps to the customer's actual telephone number. VoIP service providers, such as Vonage, typically charge customers a small monthly fee for each virtual phone number.
In find me / follow me, a user may be assigned a virtual phone number. When that number is dialed, the call may be routed among a number of phone numbers at various locations.