"Usual" functions vs function variables in JavaScript [duplicate]

I know that a difference between them is that named functions work everywhere regardless you declare them, functions in variables don't.

a();//works   
function a(){..}

works

a();//error
var a=function(){..}

doesn't work but if you call it after the declaration it works

var a=function(){..}
a();//works

This article might answer your question : JavaScript function declaration ambiguity.

Only the first one is an actual function declaration, whereas the shorthand method is just a regular variable declaration with an anonymous function assigned to it as its value.

(look at the comments, too, which might get some useful informations too)