CONS

Creates a new CONS with <car> and <cdr>.
A CONS is a basic compound data object having two components called the CAR and the CDR
A LIST is recursively defined as a CONS which CDR is a list.

Ex. (cons 'a 'b) ==> (a . b)
Ex. (cons 'a nil) ==> (a)
Ex. (cons 'a '(b c)) ==> (a b c)
Ex. (cons 'a (cons 'b nil)) ==> (a b)