What is the difference between map and apply in scheme?

Question

I am trying to learn Scheme and I am having a hard time understanding the difference between map and apply.

As I understand, map a

Answer 1

No, apply calls its first argument as a procedure, with all the rest as its arguments, with the last one -- list -- opened up, i.e. its contents "spliced in":

(apply f a b (list c d e)) == (f a b c d e)

E.g.:

(apply + 1 2 (list 3 4 5))
;Value: 15

It is just one call; whereas map is indeed calling its first argument for each member element of its second argument.

One combined use of map and apply is the famous transpose trick:

(apply map list '((1 2 3) (10 20 30)))
;Value: ((1 10) (2 20) (3 30))