Pseudo-elements ::before and ::after are special selectors that allow us to insert content before or after an element's content. We use them to add decorative elements, such as icons or borders, to an element's content without modifying the actual HTML content.

selector::before {
  /* some properties */
}

selector::after {
  /* some properties */
}

• ::before adds the content before the element content;
• ::after adds the content after the element content.

Let's consider the following example, where our task is to add some decoration for the hover effect on the links: