Difference between ":eq()" and .eq()

I have recently started learning jQuery. Considering follwing html structure, I want to know, what is basic difference between selectors $('ul>li:eq(2)') and $('ul>li').eq(2).

<ul>
    <li>one</li>
    <li>two</li>
    <li>three</li>
    <li>four</li>
    <li>five</li>
</ul>