Trigger links allow you to do things like send your contacts a link customised with their information or set "triggers" to fire when someone clicks a link.
Here's how to create them and use them.
To convert a calendar link to one that auto-fills the contact details, append the link with this:
If you're using the standard calendar (with no custom form) use this:
?first_name={{contact.first_name}}&last_name={{contact.last_name}}&email={{contact.email}}&phone=%2B{{contact.phone}}
If you've customised the calendar form to use a custom form (with full name) use this:
?full_name={{contact.name}}&email={{contact.email}}&phone=%2B{{contact.phone}}
(Note: The phone field has a %2B added in which makes sure the international code is accepted)