Two Factor Authentication (2FA) refers to situations where people must use two different classes of secret or unique information to prove their identity. The different classes of information, also called factors, are generally broken up into three categories.
Take a factor from any two of these groups and you have a 2FA solution. For example, Complyify provides users the ability to login with both a password a token. This dramatically raises the difficulty for an attacker to access a sensitive account. An attacker would need to both steal or guess the user’s password and gain physical access to their security token.