$(this)到底是获取的谁

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title></title>
    <script src="../Scripts/jquery-1.4.1.js" type="text/javascript"></script>
    <script type="text/javascript">
        var data = { "../Image/p_large_Lw04_52a70000850a5c41_副本.jpg": ["../Image/p_large_Lw04_52a70000850a5c41.jpg", "高恩灿", "18", "180"] }
        $(function () {
            $.each(data, function (key, value) {
                //创建元素节点
                var smallimg = $("<img src = '" + key + "' />");
                //给元素节点赋予属性
                smallimg.attr("bigImg", value[0]);
                smallimg.attr("personName", value[1]);
                smallimg.attr("personOld", value[2]);
                smallimg.attr("personHeight", value[3]);                smallimg.mouseover(function (e) {
                    $("#detailImg").attr("src", $(this).attr("bigImg"));
                    $("#detailName").text($(this).attr("personName"));
                    $("#detailOld").text($(this).attr("personOld"));
                    $("#detailHeight").text($(this).attr("personHeight"));
                    $("#details").css("left", e.pageX).css("top", e.pageY).css("display", "");
                });                $("#btnClose").click(function () {
                    $("#details").css("display", "none");
                });                $("body").append(smallimg);
            });
        });
    </script>
</head>
<body>
    <div style="display: none; position: absolute" id="details">
        <img id="detailImg" />
        <p id="detailName">
        </p>
        <p id="detailOld">
        </p>
        <p id="detailHeight">
        </p>
        <input type="button" id="btnClose" value="关闭" />
    </div>
</body>
</html>上面是自己看视频时做的练习，下面问题来了...下面这段代码：
smallimg.mouseover(function (e) {
                    $("#detailImg").attr("src", $(this).attr("bigImg"));
                    $("#detailName").text($(this).attr("personName"));
                    $("#detailOld").text($(this).attr("personOld"));
                    $("#detailHeight").text($(this).attr("personHeight"));
                    $("#details").css("left", e.pageX).css("top", e.pageY).css("display", "");
                });例如$("#detailImg").attr("src", $(this).attr("bigImg"));中$(this)获取的对象为什么是smalling而不是$("#detailImg")这个对象呢？还有在这里用e来替换$(this)是有错的，为什么？e和$(this)的区别在哪儿？小弟新手，望各位不要笑话...谢谢！