In this screen you can enter for this user his personal mail, SMS and Telegram user ID.
When there is a notification, the server uses these settings to determine where to send the notification.
Email: enter your email address
SMS: enter your phone number
Telegram: enter your Telegram user ID (for more information, read About Telegram)
Disable the Email, SMS or Telegram to be send to this user, by checking the Off check box.
A Super User can set the Email addresses, SMS numbers and Telegram id for all the Users also in Admin -> Change notification settings all users