What's the difference between the :nth-child and :nth-of-type pseudo classes?

nth-child will only look through child nodes. That is, any node that is inside of your selector. nth-of-type goes through the whole DOM and looks for anything that matches your selector. For instance, lets say you have this HTML:

<p>First</p>
<div>
<p>Second</p>
<p>Third</p>
</div>

Say you want to target the paragraph that contains "Second" inside of it. We can match it by using looking for children of the div or by looking through all paragraphs. Here's the CSS showing both:

div:nth-child(1) {
color: blue;
}
p:nth-of-type(2) {
color: blue;
}

They both would do the same thing, make the second paragraph in the DOM blue. The reason the number in parenthesis is different is because the paragraph we want is the second element of type "p" in the DOM as a whole, but it is the first child of the element "div".

Does that make sense?