Webflow CMS. What code does it use?

I was just wondering if anyone knows what code the webflow CMS uses ? If I were to learn a database program. Which would be best to partner with webflow CMS ? I have been sniffing around php and MySQL but reading a lot of bad stuff about those languages and databases even though they are so widely used. As I see myself growing online and using webflow for CSS and HTML. I think it’s good to understand more about there CMS and back end development plans. Any insight or discussion on code would be great for future reference.