Oh, I see what you mean. I thought you meant output HTML and templating vs server side logic, but yes, obviously I know the difference as the only front-end language is JavaScript and derivatives.
I’m more used to the terms ‘server-side’ and ‘client-side’ btw. Obviously PHP is server-side. But not all server-side is backend in my view. I consider backend to be application logic and things like database access. Templating can be done on the server or the client, and that’s front-end.
I’m sure their infrastructure includes various GOL software, like most tech/ecommerce companies. China is not known for caring much about copyright (or copyleft) and I doubt if they provide much information about that. I’m not sure why you think it would help indicate how much personal information they’re storing from people, and in any event, I think we can assume they at least store the same sort of info about customers and web visitors as sites like Amazon or Google.