rather than having a single password to authenticate, this technique adds a second piece of information for signing in
Typically your user name (or account) is the identification and your password is the authentication token. Two step authentication adds a second piece of information to the authentication step.
It is the use of two independent means of evidence (factors) to assert the identity of a user requesting access to some application or service to the organization that provides the application or service. The objective of two-factor authentication, as a method of electronic computer authentication, is to decrease the probability that the requestor is not who he/she claims to be (i.e., providing false evidence of his/her identity.)
