Autolisp, Autolisp

Neither the application programming interface nor the interpreter to execute AutoLISP code are included in the AutoCAD LT product line.

It lacks modern LISP features such as a macro system, settable list structure or let bindings. Aside from the core language, most of the primitive functions are for geometry or the manipulation of graphical entities in AutoCAD. The properties of these graphical entities are revealed to AutoLISP as association lists in which AutoCAD "group codes" are paired with values that indicate properties such as points, radii, colors, layers, linetypes, etc. AutoCAD loads AutoLISP code from .LSP files.

Vital LISP was a superset of the existing AutoLISP language that added VBA-like access to the AutoCAD object model, reactors (event handling for AutoCAD objects), general ActiveX support, and some other general Lisp functions.

Source: Wikipedia > Autolisp