Yubikey

U2F is an open authentication standard that enables internet users to securely access any number of online services with one single security key instantly and with no drivers or client software needed. Yubico

The Yubikey is inserted into the USB port of your device and when prompted, you simply touch the metal contact and a unique code is sent to the server. Upon the server receiving a code, it is verify with the Yubico servers to verify the authenticity of the key. When a correct key is provided, the key is either stored for future use or used to authenticate you are who you say you are.

FIDO U2F was created by Google and Yubico, and support from NXP, with the vision to take strong public key crypto to the mass market. Today, the technical specifications are hosted by the open-authentication industry consortium known as the FIDO Alliance. U2F has been successfully deployed by large scale services, including Facebook, Gmail, Dropbox, GitHub, and many more. The next evolution of the FIDO U2F modern authentication protocol is FIDO2 which introduces passwordless authentication capabilities.

U2F is not required for using My Authenticator and My Password, however it is highly recommended. When you set up your account, the first thing you will need to do is establish a password/pin. This password/pin is required for encryption purposes, not account purposes. You will need to occasionally need your password/pin depending your logged in status, the computer from which you are accessing your information, or any other time the system needs to identify who you are to ensure the encryption/decryption process is secure.

The U2F is being used by the server to verify you are who you say you are before you can view your data. Protects your identity. 

If you loose your Yubikey or it is no longer working, you must contact support. Support will remove the Yubikey requirement from your account and you will be able to access your data without U2F and you will then be able to add a new Yubikey.