Authentication (Auth) is the process of verifying that an individual or system is who they claim to be. It is the first step in any security process and is distinct from authorization (what a user is allowed to do).

Common methods include:

• Something you know: Passwords or PINs.
• Something you have: Security tokens, mobile phones (for OTPs).
• Something you are: Biometrics like fingerprints or facial recognition.
• Multi-Factor Authentication (MFA), which combines two or more of these methods.