LSP is a text file that contains source code written in Lisp programming language. Many dialects of Lisp exists, for example Common Lisp, Scheme, or Clojure. Lisp uses a characteristic ‘parenthesis-heavy’ syntax.

LSP code can be run using an Lisp interpreter or compiled into machine code. LSP files can contain a single stand-alone program or parts of larger software project. LSP files can be viewed using any text editor, but are commonly edited with dedicated tools that offer such features as syntax highlighting or code auto-completion.