Answer
A pseudo-class is a selector that assists in the selection of something that cannot be expressed by a simple selector, for example :hover. A pseudo-element however allows us to create items that do not normally exist in the document tree, for example ::after.
Pseudo-classes:
Pseudo-classes select regular elements but under certain conditions, like when their position relative to siblings or when they're under a particular state. Here is a list of pseudo-classes in CSS3:
a) Dynamic pseudo-classes:
- :link
- :visited
- :hover
- :active
- :focus
b) UI element states pseudo-classes:
- :enabled
- :disabled
- :checked
c) Structural pseudo-classes:
- :first-child
- :nth-child(n)
- :nth-last-child(n)
- :nth-of-type(n)
- :nth-last-of-type(n)
- :last-child
- :first-of-type
- :last-of-type
- :only-child
- :only-of-type
- :root
- :empty
d) Other pseudo-classes:
:not(x) :target :lang(language)
Pseudo-elements:
Pseudo-elements effectively create new elements that are not specified in the markup of the document and can be manipulated much like a regular element.
- ::before
- ::after
- ::first-letter
- ::first-line
- ::selection