Select Element at index = n .eq(n)

.eq(n)

e.g. $("li").eq(1)

$("selector").eq(n) selects an element at index n within the matched set.

Example 1: $("li").eq(1) will find <li> at index 1 within the matched set.
<ul>
<li>a</li> // index = 0
<li>b</li>
<li>c</li>
</ul>
Example 2: $("div").eq(2) will find <div> at index 2 within the matched set.
<div id='someID'>div-1</div> //index = 0
<p>p-1</p>
<div class='someClass'>div-2</div> //index = 1
<p>p-2</p>
<div>div-3</div> //index = 2
<span>span-1</span>
Matched set is a set of elements matching selector. For example, in Example 2 matchted set is set of elements matching $("div") selector
<div id='someID'>div-1</div> //index = 0
<p>p-1</p>
<div class='someClass'>div-2</div> //index = 1
<p>p-2</p>
<div>div-3</div> //index = 2
<span>span-1</span>
jQuery traversing filtering .eq(n)