Google Authenticator is a mobile software application that helps to authenticate the users. It is based on two-factor authentication (2FA) that provides six digit one-time password which users must provide in addition to their username and password to log into account.
In simple words, Google Authenticator is an OTP based service for secure and quick access to account.
Google Authenticator App can be downloaded from Play Store or Apple Store.
How to enable Google Authenticator in an Android Device?
How to enable Google Authenticator in an iOS Device?
How to recover g2fa onto a new mobile?