CSS Properties-the difference between pseudo-classes and pseudo-elements

Pseudo-classes and pseudo-elements are independent of the document structure. The way they get the elements is not based on the element characteristics of the ID, class, attribute, but on the element that is in a special state (pseudo-Class), or the element's special content (pseudo-element). The difference is summarized as follows:

① does not have the same wording:

css3To differentiate between the two, the pseudo-class is explicitly represented by a colon, and the pseudo-element is represented by two colons.

:Pseudo-classes::Pseudo-elements

The ② function is not the same:

 CSS Pseudo-Class (pseudo-classes): Used to add special effects to certain selectors, that is, to add special effects (usually dynamic effects) on the basis of the current static style of the element . So when an element reaches a certain state, it may get a pseudo-class style, and when the state changes, it loses the style.

Property	Describe
: Active	Add a style to the element that is activated
: Focus	Add a style to an element that has keyboard input focus
: hover	Add a style to an element when the mouse hovers over the element
: Link	Add a style to a link that is not visited
: Visited	Add a style to a link that has been visited
: First-child	Add a style to the first child element of an element
: lang	Add a style to an element with the specified Lang property

remark: In the  CSS definition, the same element: hover must be in: Link,: Visited before it takes effect: active must be in: hover before it takes effect. 

CSS Pseudo-elements (pseudo-elements): Used to set special effects to certain selectors, is to set and manipulate specific content in the element , the operation level is deeper than pseudo-class, so the dynamic is worse than pseudo-class.

	description
:first-letter	add a special style to the first letter of the text
:first-line	add a special style to the first line of text
:before	add content before element
:after	add content after element

CSS Properties-the difference between pseudo-classes and pseudo-elements