2FA, or two-factor authentication, is a way of adding additional security on your account. The first “factor” is your usual password that is standard for any account, the second is a code retrieved from an external device such as a smartphone, or a program on your computer.

It is conceptually similar to a keycode device businesses may have to use when logging into internet banking.
Two-factor authentication is a type (subset) of multi-factor authentication. It is a method of confirming a user’s claimed identity by utilizing a combination of two different factors:

1) Something they know
2) Something they have
3) Something they are

A good example of two-factor authentication is the withdrawing of money from an ATM; only the correct combination of a bank card (something that the user possesses) and a PIN (personal identification number, something that the user knows) allows the transaction to be carried out.

The use of multiple authentication factors to prove one’s identity is based on the premise that an unauthorized actor is unlikely to be able to supply the factors required for access. If, in an authentication attempt, at least one of the components is missing or supplied incorrectly, the user’s identity is not established with sufficient certainty and access to the asset (e.g., a building, or data) being protected by multi-factor authentication then remains blocked. The authentication factors of a multi-factor authentication scheme may include:

Some physical object in the possession of the user, such as a USB stick with a secret token, a bank card, a key, etc.

Some secret known to the user, such as a password, PIN, TAN, etc.

Some physical characteristic of the user (biometrics), such as a fingerprint, eye iris, voice, typing speed, pattern in key press intervals, etc.