What are "Template Tags"?
"Template Tags" is a menu at field editor, where you see available tags for use in your Calls to Action / Email Reminder(s) etc. They are available at places throughout the event when editing.
Shown below in Customize section > Email reminders when Config./Editing

You have option to choose through & associate different tags available for clients, at tabs there, or event info.

Helpful Hint:
For client's Webinar Event reminder use > Registered Date & Registered Time < separately in your email reply reminders for the time the client has chosen. (as shown above)
From the Attendee Details tab you can find specific client info. to add at other places within the webinar event.

Once setup, do not forget to test by registering to ensure all is setup well, If you have any questions in regards to Template Tags, let us know at the chatbox when logged in.
We're Happy to Help!