"Template Tags" is actually a menu in the visual editors that you see in your calls to action/email reminder customizer etc.
In template tags, you have access to different shortcodes that you may need.
Registrant Name
Webinar Title
Today's Date MM/DD/YY
Today's Date DD/MM/YY
Today's Date, no year
Today's Date, with year
Today's Weekday
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utm_source
utm_medium
utm_campaign
utm_term
utm_content