Two Factor Authentication is an added layer of security for your Apple ID. By enabling tow factor authentication, you can be assured that, you are solely accessing your account. It protects your account by requiring a password and access to either a verification code delivered via phone call or SMS or a trusted device. Starting February 27, 2019, Apple has made it mandatory to have two factor authentication to sign in to your Apple Developer account and Certificates, Profiles & Identifiers.
Enabling Two Factor Authentication
To enable “Two Factor Authentication” for your Apple ID, you need to follow the steps mentioned in the Apple’s help link.