css pseudo class and code example

Example 1: What is a pseudo selector?

A pseudo-class is a selector that selects elements that are in a specific state, e.g. they are the first element of their type, or they are being hovered over by the mouse pointer

Example 2: css pseudo classes

button/anchor:hover / :active / :checked
:nth-of-type(3) // select the third element
:nth-of-type(3n) // select an element every three