Emacs Lisp

From Rosetta Code

Emacs Lisp (often abbreviated to elisp) is the Lisp implementation used by the Emacs text editor. It doesn't provide all features of Common Lisp (e.g. its optional arguments always default to nil), but it contains special types which are specific for the use in the editor, like buffers (which is where you actually edit the text), windows, events etc.

Lisp expressions can be executed directly from within Emacs editor buffers, or loaded from files which optionally can be compiled into bytecode.

Emacs configuration files actually are Emacs Lisp source files.