defun-q vs defun

Would someone please give me an didiots guide to the difference between defun-q and defun.

I've seen a few routines of late written with defun-q instead of defun. Most also seem to be missing the C: after the defun. ie "defun-q my-lsip" not "defun-q c:my-lisp".

Thanks in advance

In simple terms, defun-q defines a function as a LIST type which may therefore be subsequently manipulated as such; defun defines a function as a subroutine (SUBR)/user-subroutine (USUBR) type, whose definition is no longer exposed and can therefore only be redefined, not modified.

Questioning the absence of a c: prefix in a function definition is a far more basic question: the c: prefix simply makes a function symbol available for direct evaluation at the AutoCAD command-line - not all defined functions are intended to be called at the command-line by the user, but rather by other functions within an application.