What is a two-factor authentication?

A two-factor authentication describes any authentication mechanism that requires two components to identify and authenticate a user. The two factors involved are usually spoken of as something you know (a user name and password) and something you have (a security token, a physical token in a card, etc.).

 Using a username and password together with a token that only the user has makes it harder for potential intruders to gain access and steal that person’s personal data or identity.