rich text is the result of adding metadata information to plain text in order to add functionalities such as styling.
Rich text is also known as styled text where styled does not stop at the font and can be any visual such as a complete graph.
When everything except primary content is removed from rich text, only plain text should remain.
That the term Google Rich Result comes form
Examples of information that can be added include:
Rich text languages are almost exclusively created in all markup languages such as
And of course, they may be serialized also in JSON, XML, …