FIDO is a set of technologies agnostic protocols used to provide simple and strong authentication. The latest version is FIDO2 which uses CTAP and WebAuthn enables users to leverage common devices to authenticate to online services and both mobile & desktop.
Fido is supported natively by all major browsers and online service providers such as Microsoft, Google and Amazon just to name a few. They also provide how-to documents to help configure fido keys to work as secure password-less authenticators on their platforms. FIDO2 a solution that can be leveraged to implement zero trust initiatives.
This image illustrates how FIDO facilitates authentication from user to online services and other devices
To learn more about FIDO check out fido-Alliance