【jQuery】変数の意味を知りたいです。

スワイプ実装で変数d={x:undefined,thisX:undefined,startX:undefined,moveX:undefined};と書く意図が分からなかったので教えていただきたいです。
動作はできています。

html
1<!doctype html>
2<html>
3<head>
4<meta charset="UTF-8">
5<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
6<meta name="format-detection" content="telephone=no">
7<title></title>
8<link rel="stylesheet" href="css/reset.css">
9<link rel="stylesheet" href="css/base.css">
10<link rel="stylesheet" href="css/style.css">
11</head>
12<body>
13<div class="swipe-photo">
14    <ul class="swipe-photo-container clearfix">
15        <li class="swipe-photo-item"><img src="img/0.jpg" class="swipe-photo-thumbnail"></li>
16        <li class="swipe-photo-item"><img src="img/1.jpg" class="swipe-photo-thumbnail"></li>
17        <li class="swipe-photo-item"><img src="img/2.jpg" class="swipe-photo-thumbnail"></li>
18        <li class="swipe-photo-item"><img src="img/3.jpg" class="swipe-photo-thumbnail"></li>
19        <li class="swipe-photo-item"><img src="img/4.jpg" class="swipe-photo-thumbnail"></li>
20        <li class="swipe-photo-item"><img src="img/5.jpg" class="swipe-photo-thumbnail"></li>
21    </ul>
22</div>
23<script type="text/javascript" src="js/jquery.js"></script>
24<script type="text/javascript">
25</script>
26</body>
27</html>
28

該当のコード

script
1$(function(){
2	  var b=$(".swipe-photo"),
3	  f=b.find(".swipe-photo-container"),
4	  j=b.find(".swipe-photo-item"),
5	  e=j.find(".swipe-photo-thumbnail"),
6	  h=e.width(),
7	  a=j.length,
8	  k=[],
9	  d={x:undefined,thisX:undefined,startX:undefined,moveX:undefined};
10
11	  for(var c=0;c<=a;c++){
12	    k[c]=-c*h
13	  }
14
15	  $(".swipe-photo-container").width(h*a);
16
17	  j.on({touchstart:function(i){
18	    d.thisX=parseInt($(".swipe-photo-container").css("left"));
19	    d.startX=i.originalEvent.changedTouches[0].pageX-d.thisX
20	  },
21
22	  touchmove:function(i){
23	    i.preventDefault();
24	    d.x=i.originalEvent.changedTouches[0].pageX;
25
26	    if(d.x-d.startX>=0){
27	            d.moveX=0
28	    }else{
29	      if(d.x-d.startX<=k[a-1]){
30	        d.moveX=k[a-1]
31	      }else{
32	        d.moveX=d.x-d.startX
33	      }
34	    }
35	    $(".swipe-photo-container").css({left:d.moveX})
36	  },
37
38	  touchend:function(n){
39	    var m="";
40
41	    for(var l=0;l<a;l++){
42	      if(k[l]+(h/2)>d.moveX&&d.moveX>=k[l+1]+(h/2))
43	        {m=l}}
44	        $(".swipe-photo-container").animate({
45	        left:k[m]
46	        },400)}
47	    })
48    });

共通CSS

css
1.swipe-photo {
2    position: relative;
3    width: 320px;
4    height: 240px;
5    margin: 0 auto;
6    overflow: hidden;
7}
8.swipe-photo-container {
9    position: absolute;
10    top: 0;
11    left: 0;
12}
13.swipe-photo-item {
14    float: left;
15}
16.swipe-photo-thumbnail {
17    width: 320px;
18    height: 240px;
19}