Google Authenticator is a mobile app that provides an extra layer of security for online accounts. It generates time-based one-time passwords (TOTPs) that users enter along with their regular passwords. This two-factor authentication (2FA) helps protect accounts from unauthorized access, even if someone knows the password. The app is available for both Android and iOS devices. Users can set it up by scanning a QR code provided by the service they want to secure. Once configured, the app generates a new code every 30 seconds, ensuring that only the user can access their account.