It is worth noting that the more fundamental thing going on here is that abstract syntax trees are the general way in which programs are represented after being parsed, rather than this being something specific to Lisp. What makes Lisp interesting is essentially that it uses a notation that makes the underlying AST incredibly explicit.

wow such a great post! I loved how simply and like he said, intuitively he explained this. This really highlights how goo S-expressions and lisp syntax is.