Vishing is a scheme. This scheme is also known as “voice phishing.” It occurs when the thief contacts an individual over the telephone.
In this instance, the schemer poses as an individual working for a legitimate organization such as a government agency, a financial institution, a payment services organization, or another well-known company.
The goal is to get you to disclose your personal identifying information. Another tactic used is to make robo-calls (prerecorded messages) urging you to contact a certain phone number, stating that you either won a prize, or an emergency has occurred that requires you to disclose your personally identifiable information or credit card / debit card numbers.
Ref.: http://www.utica.edu/academic/institutes/cimip/idcrimes/schemes.cfm