When these people talk about 'Lisp', they mean Lisp 1, Lisp 1.5, Maclisp, Standard Lisp, Emacs Lisp, Lisp Machine Lisp, Common Lisp, ISLisp, Autolisp, ... All

When these people talk about 'Lisp', they mean Lisp 1, Lisp 1.5, Maclisp, Standard Lisp, Emacs Lisp, Lisp Machine Lisp, Common Lisp, ISLisp, Autolisp, ... All these languages are somewhat compatible with the original Lisp 1. Then there is the wider Lisp family which includes Scheme, Dylan, Clojure, ECMAScript, Racket, SKILL, Hop, Logo, ...