Two-factor authentication is a mandatory security requirement (from PSD2) to protect electronic payments and other related services. 

Your identity is verified by validating at least 2 of the following 3 criteria: 

• An element that you have created to secure your account (personal code, secret question...)
• An element that you have in your possession (mobile, identity card...)
• An element that characterizes you (biometrics: fingerprint, facial recognition...)