When you receive a call on your phone from an unknown number, it's nearly impossible to guess who's calling. Increasingly, it could be someone vishing you.   
Vishing is a term derived from "phishing" and "voice." Just like phishing involves malicious emails, vishing is a phone scam that is designed to compel you to provide your personal information.
Here's what you need to know about vishing scams, and how you can identify and avoid them.