How to use map and apply

How to use map? For example, I have a function

(map string-length

(list “cat” “dog” “fish” “banana”))

I simply do

(list (string-length “cat”) (string-length “dog”) (string-length “fish”) (string-length “banana”))

The answer will be

(list 3 3 4 6)

This is how we use map, we bring all the listed elements into the function and return a new list.

How to use apply? For example, I have a function,

(apply string-append

(list “cat” “dog” “fish” “banana”))

I simply do

(apply string-append

 “cat” “dog” “fish” “banana”)

The answer will be

(catdogfishbanana)

This is how we use apply, we bring all the elements into one function and return it together.