The init function - creates the model with default values and uses it as part of the command that retrieves the categores

Conspiracies.elm

-- init does what you might think it does, it initializes the applicaiton.
-- In this app, I need to fetch the list of tags when the page loads so 
-- the user has some navigation to work with so I make the call to the
-- httpCommand function.
init : ( Model, Cmd Msg )
init = 
    let model = { categories = []
                , errorMsg = Nothing 
                , selectedTag = "All"
                , summaries = []
                }

    in 
        ( model,  getCategoriesCommand) 
        
 .......... some other code ..........

main : Program Never Model Msg
main =
    program
        { init = init
        , view = view
        , update = update
        , subscriptions = \_ -> Sub.none
        }