Pseudo-elements are added to selectors but instead of describing a special state, they allow you to style certain parts of a document.

The content attribute is required for pseudo-elements to render; however, the attribute can have an empty value (e.g. content: "").

div::after {
  content: 'after';
  color: red;
  border: 1px solid red;
}

div {
  color: black;
  border: 1px solid black;
  padding: 1px;
}

div::before {
  content: 'before';
  color: green;
  border: 1px solid green;
}