This is the "closure/object isomorphism", basically.

The outer function (cons) is a class constructor. It returns an object, which is a function of one argument, where the argument is equivalent to the name of a method. In this case, the methods are getters, so they evaluate to values. You could just as easily have stored more procedures in the object returned by the constructor.

In this case, numbers where chosen as method names and sugary procedures defined outside the object itself. You could have used symbols:

    (define (cons x y)
      (lambda (method)
        (cond ((eq? method 'car) x)
              ((eq? method 'cdr) y)
              (else (error "unknown method")))))

In which case what you have more closely resembles OO:

    # (define p (cons 1 2))
    # (p 'car)
    1
    # (p 'cdr)
    2