Two-Factor Authentication (2FA) is a security process that requires users to provide two means of identification before accessing their account.
The two levels of security add to your password a unique special code generated by an authentication app installed on your smartphone or pc. Two popular apps are Google Authenticator and Authy.
If you have 2FA enabled you will receive a temporary 6 digit code which can be used only for a short period of time about 20 seconds, the code will expire and a new code will be generated.
This requirement makes your account better protected, your account cannot be accessed without direct access to your authenticator app.
Do not forget to save your 2FA Secret Key to recover your 2FA in case you will love your laptop/mobile.