(* 3 4)                 ; equivalent to pseudo-code *(3, 4).
                        ; Symbol '*' is a function
                        ; 3 and 4 are its parameters.
                        ; Returns 12.
(times-two 5)           ; returns 10
(3 4)                   ; error: 3 is not a function
(times-two)              ; error, times-two expects one parameter
(times-two 3 4)          ; error, times-two expects one parameter
(set + -)               ; sets symbol '+' to be equal to whatever symbol '-'
                        ; equals to, which is a minus function
(+ 5 4)                 ; returns 1 since symbol '+' is now equal
                        ; to the minus function
(* 3 (* 2 2))           ; multiplies 3 by the second parameter
                        ; (which is a function call that returns 4).
                        ; Returns 12.