The differences between procedures with and without brackets?

Question

(define (procedere1) (lambda () 2))
(define procedure2 (lambda () 2))

They both can be compiled. But I am confused about the difference between above two procedures.

Answer 1

The first one is a procedure that returns a procedure. The second one is a procedure that returns the number 2.

In particular, the first one is equivalent to the following:

(define procedure1
  (lambda ()
    (lambda () 2)))

Answer 2

In general

(define (name arg1 arg2 arg3 ...)
  body)

is shorthand for

(define name
  (lambda (arg1 arg2 arg3 ...) 
    body))