What language used in Ebay Templates?

Greetings All,
Well, I've been trying and trying to figure this out myself, but am hoping someone can end my confusion by explaining to me one simple thing.

I understand that ebay users are using HTML to edit the provided ebay storefront templates...but what language are designers using to program the customized templates they sell on ebay to ebay store owners? Obviously, some of it would be HTML, but what language is used to create the fields that the store owner then fills in to 'fill in the blanks' with their own information? This is what I am so eager to understand. I would greatly appreciate a reply!!

 

It's all html. Some most likely use a little JS, but what you've described is all html stuff. html and JS is all you can use on ebay.