Questions about Elm language

gistfile1.txt

https://guide.elm-lang.org/effects/http.html

main =
  Browser.element
    { init = init
    , update = update
    , subscriptions = subscriptions
    , view = view
    }


Questions about:
init = init

First init:  a variable expected by Browser.element function?
Second init: a function declared in my program?

etc. for update, subscription, view.

---------------------------------------------------------------

init : () -> (Model, Cmd Msg)
init _ =
  ( Loading
  , Http.get
      { url = "https://elm-lang.org/assets/public-opinion.txt"
      , expect = Http.expectString GotText
      }
  )

init : () -> (Model, Cmd Msg)
Is sort of:

function init() {
	.... 
	return (Model, Cmd Msg)
}

What is Cmd Msg . I'm returning a Model AND Cmd Msg
However, Cmd Msg represents two variables? 

Why not init : () -> (Model, Cmd, Msg)
How are the two different? 

-------------------------------------------------------------

update : Msg -> Model -> (Model, Cmd Msg)
update msg model =
  case msg of
    GotText result ->
      case result of
        Ok fullText ->
          (Success fullText, Cmd.none)

        Err _ ->
          (Failure, Cmd.none)

How is (Success fullText, Cmd.none) the same as (Model, Cmd Msg) ? 
Specifically how is  Cmd.none the same as Cmd Msg

Success fullText is what Model returns so that's clear, but Cmd.none? What is Cmd.none :)