var sliderNav = function(manual){
   function body
}

vs

function sliderNav(manual){
    function body
}

Are these two ways just for declaring functions or is there something else going on here that I'm unaware of?

Since there are no return types here, can I assume they are related to return types in some other way maybe? (Since as per my knowledge, when assigning a function to a variable, we are primarily assigning to it what the function is returning.)