Passwords are reused, guessed and stolen, and even careful users struggle to manage dozens of them. Passkeys replace the typed secret with a cryptographic key stored on your device, unlocked by a fingerprint, face or PIN, so there is nothing to remember or type.
The key never leaves your device in a usable form, and each site gets a different one, so a leak at one service cannot unlock another. The trade-off is managing recovery when a device is lost, which is why passkeys are usually synced or backed up across a user's devices.