Lisp is very good at parsing language (i.e. all data, like computer programs, are read into lists and LISP is built around this functionality; this is one reason why it is very popular among AI researchers). Combine that with things like 'eval' statements and you can easily parse and execute an arbitrary computer language with LISP. Very, very cool stuff.

EDIT: Here's a good explanation of why LISP is good at this sort of thing: http://jlongster.com/2012/02/18/its-not-about-macros-its-abo...