Definition
A passkey is a discoverable FIDO2 credential designed to replace passwords for everyday authentication — typically syncable across a user's devices via a platform credential manager (Apple Keychain, Google Password Manager, 1Password, etc.).
Passkeys are the consumer-friendly packaging of FIDO2 / WebAuthn. They're "discoverable credentials" — the authenticator can list them to the user without requiring a username first. They're typically syncable across a user's devices via cloud-based credential managers, removing the device-loss objection that limited earlier FIDO2 adoption.
For enterprises, passkeys span two flavors: platform passkeys (built into Touch ID / Windows Hello / phone biometric) and security-key passkeys (USB/NFC keys). Both are phishing-resistant; platform passkeys are more user-friendly, security keys offer stronger device-bound guarantees.