What is in the standard library?

There is a standard library in julia v1.0. How can I get the list of modules in that library?

I am also a bit confused by Iterators.

julia> join(names(Iterators), " ")
“Iterators countfrom cycle drop enumerate flatten partition product repeated rest take zip”

julia> apropos(“Iterators”)
… long list containing functions not in the previous list: Iterators.filter, Iterators.peel, Iterators.reverse but not Iterators.enumerate.

The documentation, perhaps?

The module, or the concept?

I wish to list the modules installed in the standard library from a program.