x.map(f) doesnt mean "apply function f to each element in this list that we called x"

x.map(f) means "apply the function f to the value within x, where x is a container of some sort"

[].map(f) would do nothing, because there is nothing to pull out.

['adam', 'bill'].map(f) takes 'adam' out of the array, applies f to it, and puts it back in the array, then does the same with 'bill'.

Just(5).map(f) takes 5 out of the Maybe, applies f to it, and puts it back in

nothing.map(f) returns nothing.

So we can map functions to values in Arrays, map functions to values in Maybes and even map functions to values in Eithers. Each time the function doesnt care that the value is in a Maybe or an Array or an Either.