Default Bootstrap Navbar in Elm

Nav.elm

module Nav exposing (..)

import Html exposing (Html, div, a, span, i, ul, li, nav, button, text, form, input, header)
import Html.Attributes exposing (class, id, href, placeholder, attribute, type')


navbar : Html msg -> Html msg
navbar links =
    header []
        [ nav [ class "navbar navbar-default" ]
            [ div [ class "container-fluid" ]
                [ div [ class "navbar-header" ]
                    [ mobileToggleButton
                    , navbrand "#" "Brand"
                    ]
                , links
                ]
            ]
        ]


navbrand : String -> String -> Html msg
navbrand url brandName =
    a [ class "navbar-brand", href url ] [ text brandName ]


mobileToggleButton : Html msg
mobileToggleButton =
    button [ type' "button", class "navbar-toggle collapsed", attribute "data-toggle" "collapse", attribute "data-target" "#bs-example-1", attribute "aria-expanded" "false" ]
        [ span [ class "sr-only" ] [ text "Toggle Navigation" ]
        , span [ class "icon-bar" ] []
        , span [ class "icon-bar" ] []
        , span [ class "icon-bar" ] []
        ]


navbarLinks : Html msg
navbarLinks =
    div [ class "collapse navbar-collapse", id "bs-example-navbar-collapse-1" ]
        [ ul
            [ class "nav navbar-nav" ]
            [ li [ class "active" ] [ a [ href "#" ] [ text "Link", span [ class "sr-only" ] [ text "(current)" ] ] ]
            , li [] [ a [ href "#" ] [ text "Link" ] ]
            , li [ class "dropdown" ]
                [ a [ href "#", class "dropdown-toggle", attribute "data-toggle" "dropdown", attribute "role" "button", attribute "aria-haspopup" "true", attribute "aria-expanded" "false" ]
                    [ text "Dropdown", span [ class "caret" ] [] ]
                , ul [ class "dropdown-menu" ]
                    [ li [] [ a [ href "#" ] [ text "Action" ] ]
                    , li [] [ a [ href "#" ] [ text "Another action" ] ]
                    , li [] [ a [ href "#" ] [ text "Something else here" ] ]
                    , li [ attribute "role" "separator", class "divider" ] []
                    , li [] [ a [ href "#" ] [ text "Separated link" ] ]
                    , li [ attribute "role" "separator", class "divider" ] []
                    , li [] [ a [ href "#" ] [ text "One more separated link" ] ]
                    ]
                ]
            ]
        ]

Knowing nothing about this language, but a bit about statically-typed languages... I still don't know what this does: https://gist.github.com/glinesbdev/47c50795bb5a1903fa5c9e9d1f4512f0#file-nav-elm-L22

The HTML this outputs can be found here: https://gist.github.com/glinesbdev/0c3fc6bcadf42e115b0bcf39b2b06b63