Final answer:
The User Activation screen in DTS is shown during initial account setup or when a reactivation is required, used for security and profile setup.
Step-by-step explanation:
The Defense Travel System (DTS) displays the User Activation screen at the start of your DTS usage when you create an account or when your account requires reactivation due to inactivity or system updates. At this screen, you'll be prompted to provide personal information to confirm your identity and to set up necessary components of your profile, such as authentication details. This process is crucial for maintaining security and ensuring that only authorized users have access to the DTS.