Two factor authentication is login process that requires two out of the three elements described below:
Something You Know
This is typically a password or a PIN code you memorize
Something You Have
This is usually a card, ID badge, or a piece of hardware like your phone
Something You Are
This can be a finger or palm print
Duo uses your smart phone as a second factor to strengthen our existing authentication system. Detailed questions about Duo Security’s implementation of two factor authentication can be found
here.