CSS3 pseudo-class, pseudo-element selector---nth-child () and Nth-of-type () selectors

P:nth-child (2)	To satisfy two conditions, 1: The second child element of the parent element of the P element is selected
	2: The second child element of the selection must be a P element and will not be displayed if it is not satisfied

P:nth-of-type (2)

Select the second P element under a parent element

CSS3 pseudo-class, pseudo-element selector---nth-child () and Nth-of-type () selectors