Here are some examples of text features from an article and how they help understanding:
Table of Contents: Lists the major sections "Introduction", "History", "Current Status" which helps me know what topics will be covered.
Subheadings: "Early Development" and "Advances in Technology" within the History section divide that information and signal what each part is about.
Photograph: Shows an image of the subject which helps put a face to the name and understand what it looks like.
Caption: Explains what is happening in the photo and provides context to help interpret it.
Diagram: Illustrates the inner workings in a visual way which complements the written explanation.
Glossary: