A visualization is just a picture based on data. Any time you take data and turn it into a picture, you've created a visualization.
As Economic and Industrial Delusions: A Discussion of the Case for Protection, Farquhar, Arthur B—a classic book from the 19th century—puts it:
"The graphical method has considerable superiority for the exposition of statistical facts over the tabular. A heavy bank of figures is grievously wearisome to the eye and the popular mind is as incapable of drawing any useful lessons from it as of extracting sunbeams from cucumbers"
But there is a world of difference between charts and graphs of old and the visual masterpieces from the examples gallery of d3.js. The new medium lets us do so much more with data that the growth in popularity of visualizations is hardly surprising.
Compared to a good modern visualization, a chart barely goes beyond showing raw data. It doesn't tell you anything, but a visualization does.
You don't even have to go full...