An authenticator app is a security tool that generates temporary, time-based codes to verify your identity when logging into accounts. It adds an extra layer of protection beyond your password, making it harder for hackers to access your accounts. To use it, you download an app like Google Authenticator or Microsoft Authenticator, scan a QR code provided by the website or service, and then enter the code from the app each time you log in. This ensures that even if someone knows your password, they can’t access your account without the code.