It might help if you stated the context in which you came across the term.
Given that you asked about FIDO and FIDO2 I assume you mean the authentication protocol. [https://en.wikipedia.org/wiki/FIDO2_Project](https://en.wikipedia.org/wiki/FIDO2_Project)
It might now help if you said what parts you wanted explained, since there’s a lot there and it’s somewhat complicated.
It might help if you stated the context in which you came across the term.
Given that you asked about FIDO and FIDO2 I assume you mean the authentication protocol. [https://en.wikipedia.org/wiki/FIDO2_Project](https://en.wikipedia.org/wiki/FIDO2_Project)
It might now help if you said what parts you wanted explained, since there’s a lot there and it’s somewhat complicated.