the formals list of a macro definition

(x y z)
(x y z &optional max (base '10 basep))
(x y &rest rst)
(x y &key max base)
(&whole sexpr x y)

The ``lambda-list'' of a macro definition may include simple formal parameter names as well as appropriate uses of the following lambda-list keywords from CLTL (pp. 60 and 145), respecting the order shown:

  &key, and
ACL2 does not support &aux and &environment. In addition, we make the following restrictions:

(1) initialization forms in &optional and &key specifiers must be quoted values;

(2) &allow-other-keys may only be used once, as the last specifier; and

(3) destructuring is not allowed.

You are encouraged to experiment with the macro facility. One way to do so is to define a macro that does nothing but return the quotation of its arguments, e.g.,
(defmacro demo (x y &optional opt &key key1 key2)
  (list 'quote (list x y opt key1 key2)))
You may then execute the macro on some sample forms, e.g.,
  term                         value
(demo 1 2)                (1 2 NIL NIL NIL)
(demo 1 2 3)              (1 2 3 NIL NIL)
(demo 1 2 :key1 3)        error:  non-even key/value arglist
                          (because :key1 is used as opt)
(demo 1 2 3 :key2 5)      (1 2 3 NIL 5)
Also see trans.