In the examples, any bold stuff is the result of running the code above it.
This is a list:
(apple orange banana)
Lists can be nested:
((fruit (apple orange banana)) (colour (red green)))
Lisp usually interprets lists as function calls:
(+ 40 2) 42
Lisp usually interprets symbols (i.e. identifiers) as variable references:
(* pi 2) 6.2831853071795862
A single-quote character "quotes" something, i.e. prevents Lisp from interpreting it. So the following is a list of symbols:
'(elem1 elem2 elem3)
let creates a list of variables that can be used in an expression:
(let ((a 1) (b 2) (mylist '(a b))) expression)
Hereafter, a will be 1, b = 2, mylist will contain the list '(a b).
setq changes the value of a variable:
(setq mylist '(a b c))
The cons function makes a pair:
(cons 'first 42)
Cons pairs are usually used to make lists: the first element is the first element on the list; the second element is either a cons pair for the rest of the list or a nil to mark the end of the list. Consider the following list:
'(1 2 3)
This list is a shorthand for:
(cons 1 (cons 2 (cons 3 nil)))
car returns the first element of a list:
(print (car mylist)) a
cdr returns the rest of the list (ie all-but-first):
(print (cdr mylist)) (b c)
And that is basically LISP.
The following example is an inefficient factorial function:
(defun fact (x) ;a recursive function (if (> x 0) (* x (fact (- x 1))) 1))
Look for the tutorial links on the LISP page.