|This is another name for your linked email. ATA ID is one of two ways to link your account so that you can access it on other devices, or if you ever log out or unlink your device.
To set one up, go to Settings > Account Management > ATA ID
You can create an ATA ID with a password or without one (using email link). Your email will need to be verified to get a free DN.
NOTE: your email must be valid, as password reset links are sent to that email!