App Passwords help you to connect to finance applications and services (such as Mint and TurboTax) for convenience and productivity in a safer way.

When using App Passwords, these services will only have the ability to view your account balance and other financial transaction information, without the ability to make changes to your account. This way, you can take advantage of the benefits with an additional level of security.

Consider using App Passwords with any outside applications you connect to your Betterment account.
From your Security tab, you should also consider periodically reviewing the third-party services you’ve granted access to your Betterment account, and revoke access from any applications or services that you no longer want to provide access to.