What text is included in the visualization?
The whole point of a visualization is to convey information visually--through color, placement, shape, size, and so on. However, text also functions importantly in most infovis projects in the form of labels, annotations, explanations, other commentary. Text can focus attention on certain areas and begin to direct interpretation. Textual elements can also establish ethos by citing sources or indicating limitations of data or other uncertainties. Text can also often convey information in a way that visual elements can't--for instance, through allusions, puns, metaphors, and cultural references.
Writing teachers are in familiar territory when we ask students to analyze the textual elements in an information visualization.
It's instructive to strip away text from a graphic--in this case, one taken from CNN Money, to see the role that text plays.
The graphic is impossible to understand without any textual labels or explanations.
Adding a title and two labels allows readers to understand the point of the graphic.
Additional textual information--title, author, source, source of data, explanation, social media markers-- begin to direct interpretation of the graphic.