What are the pseudo-classes in CSS3?

see the response in

https://www.w3schools.com/css/css_pseudo_classes.asp

A Pseudo class in CSS is used to define the special state of an element. It can be combined with a CSS selector to add an effect to existing elements based on their states. For Example, changing the style of an element when the user hovers over it, or when a link is visited. All of these can be done using Pseudo Classes in CSS.

• A pseudo-class is used to define a special state of an element.For example, it can be used to change the color of a selected link
• Syntax

selector:pseudo-class {  property:value;}

• Example:/* unvisited link */a:link {  color: #FF0000;}/* visited link */a:visited {  color: #00FF00;}

A pseudo-class is used to define a special state of an element.

For example, it can be used to:

• Style an element when a user mouses over it
• Style visited and unvisited links differently
• Style an element when it gets focus

A CSS pseudo-class is a keyword added to a selector that specifies a special state of the selected element(s). For example, :hover can be used to change a button's color when the user's pointer hovers over it.

/* Any button over which the user's pointer is hovering */

button:hover {    color: blue;}

Syntax

selector:pseudo-class {    property: value;}

From my point of view, pseudo-classes in css3 can be used to define a special stateof  an element, e.g when the user trys to hover a mouse on top of an element where it can change color

Pseudo-class also can be used to define special rules for different languages.