Edit in JSFiddle

<div id="callback">This is example for callback functions !!</div>
<input type="button" id="click" value="Hide" />

$(document).ready(function () {
    $("#click").click(function () {
        $("#callback").hide("slow", showAlert);
    });

    function showAlert() {
        alert("Hide operation completed !!");
    }
});

#callback {
    height:100px;
    width:200px;
    background-color:Green;
}