2FA
In plain terms
Two-factor authentication, a common form of MFA.
Going deeper
2FA requires exactly two factors, typically a password plus a one-time code or device, to confirm identity. It blocks attackers who only have your password.
Under the hood
App-based or hardware codes are far safer than SMS; a subset of MFA.
Examples
Authenticator apps, SMS codes, YubiKey, account protection.
Think of it like...
Like an ATM needing both your card and your PIN.