A Primitive is a NetLogo command, reporter, or other word or symbol built-in to NetLogo. In other languages such words might be called “reserved words”, “built-ins”, or “internals”. Any NetLogo code word that is not “user-defined” or provided via the NetLogo JAVA API, is a primitive.
A word is “primitive” in contrast to “user-defined”. In NetLogo, it is possible to create user-defined commands, reporters, breeds, and variables
See the primtive dictionary for the list of all NetLogo primitives.