Final answer:
The Duo Mobile app is used for two-factor authentication, providing an extra layer of security that requires a second form of verification beyond just a password.
Step-by-step explanation:
The Duo Mobile app is primarily used for two-factor authentication. This enhanced security feature adds an additional layer of protection beyond a simple username and password by requiring users to provide a second piece of information before they can gain access to their account. This could be a code generated by the app, a phone call, or a text message with a code. By having two-factor authentication enabled, individuals and companies can greatly reduce the risk of unauthorized access to sensitive information, thus increasing security for users.