# pseudo-class
`p:first-child` behaves as if you added a class to the first p element, these are known as pseudo-class selectors.
# pseudo-element
pseudo-element selectors act as if an element was dynamically inserted, for example `::first-line` acts in a similar way to you wrapping a span around the first line of text.
https://www.smashingmagazine.com/2019/01/how-to-learn-css/