[jQuery] Callback Function > had a look but don't get it

Ok i'm nearly there LOL

i have the link and a box which i want to foundOut as my function.

All works dandy now :)

But whatif i wanted after i clicked on the link to go to its normal
state?

Well i went to the jquery site but i don't think its designed for TRUE
beginners like myself....

It talks about Callback function and its displayed like this

function callback() {
this; // dom element
}

So here is my code and where do i put this callBack? and do i need to
add a class to it?
$(function() { // document is ready for load
$('a').click(function() {
$('.box').fadeOut("slow");

});
});

Jessie