https://finance.yahoo.com/news/google-launches-advanced-gmail-security-111502794.html

The advanced protection features include an option to require a physical USB security key to connect to a desktop computer before each log-in as a way to verify a user's identity. Mobile log-ins will require a Bluetooth wireless device.

Advanced protection users will have their data walled off from access by any non-Google third-party applications, such as the Apple iOS mail client or Microsoft Outlook.