It is Clojurescript. It is just a vector that contains a keyword, map and string. The Hiccup library would convert that to HTML but at the end of the day, it is all Clojure(Script) data structures.

Yes, but the Hiccup library works with both Clojure and ClojureScript.

Edit: I guess it’s the Hiccups port that works for Cljs. Either way hiccup notation is standard for both.