A tech service named Clerk put together a nice breakdown of how Passkeys work on a technical level. I've found many other explanations too focused on technical definitions rather than a conceptional overview or so simplistic they were unhelpful for me. This one feels like a nice balance between not enough information and too much.

The article is broken down into the sections below:

• What are passkeys?
• How does public key crypto work?
• A practical use of public-key cryptography
• How are passkeys more secure than a username and password?
• Clerk supports passkeys [this last section is irrelevant to anyone not interested in the service provided by Clerk]

Clerk provides some sort of user management service; I don't know nor care if it's any good.