Hi
The Trigger Class Selector is a way of launching the modal from elements already on the page. Say you have an existing title on the page that when clicked on you want to launch your modal. If you inspect the page code for the title hopefully it’s got a unique class associated with it. You would then use this class name in the Trigger Class Selector field. The way this works behind the scenes, is that the code assigns a click trigger event to the class entered in the Trigger Class Selector field, so when the title is clicked on the modal is displayed.
Hope this helps.