RTF

RTF stands for “Rich Text Format”. It is a binary format (in opposition to plain text formats such as HTML, Markdown and LaTeX).

By being binary it is not editable but hand and hence can be a more complex format as it requires tools to update the text.

It has more advanced functions (such as LaTeX) but the format is applied locally to each part of the text. Some tools (most of the modern ones) allows creating styles and updating them as part of its interface, so you don't have to style things individually.

It is used for a few tasks and was commonly used by different tools to interchange information between their non-compatible proprietary formats.