Two-Factor Authentication - security process requiring two different authentication methods. Like needing both an ID and a secret handshake to enter a club.
Gmail 2FA requires your password plus a code from your phone to sign in from new devices.
All four clouds support 2FA/MFA primarily through their identity services. AWS IAM, Microsoft Entra ID, Google Cloud Identity, and OCI IAM can require a second factor (app code, push, hardware key) in addition to a password when users sign in to consoles, portals, or federated apps.