Create your wallet
Testnet: this chain resets when the protocol changes. Funds have no value.
Your browser saves a passkey for zapp-testnet.duckdns.org. The passkey signs for your account, so keep it on a device you lock.
Where the passkey is kept
Your browser or phone decides: iCloud Keychain, Google Password Manager, Windows Hello, or a security key if you pick one in its window.
Passkey saved
Check your passkey
One more touch signs a test, so the wallet knows this passkey works before any money depends on it. Browsers allow one passkey request per press, which is why this is a second step.