Storing HTML within database and utilizing w/ dynamic pages

@theredeng wondering if you can help me out in understanding the original code that girlzano posted. Specifically - what goes here in the code on the HTML element:
getElementById(“whatevernameinsidedivs”).innerHTML = event.data;

Very new to coding so not sure if that is the field name from the database or something else. Also, did you use a plain text field in the database to store your HTML? THANKS in advance!