What is a "brush"?

Question

The docs go right into the details of using the "brush" API without ever describing what a "brush" is.

I can make my own educateded guesses, of course, based on the examples given in that page, but I'm looking for a more formal introduction to what a "brush" is.

(Searching for "brush", or even for a combination such as "brush" and "graphics", has not very effective for me, because the term "brush" is already widely used in the area of graphics software to denote something entirely different (e.g. AI's brush shapes, etc.).)

In particular, I'd like to know: Is "brush" d3.js-specific terminology, or a even a d3.js-specific idea? Also, what are "brushes" good for? And what are they not good for? (Maybe I'm denser than the average, but I don't find the word-less examples given in the d3.js site particularly helpful with these questions.)

Answer 1

OK, I found what I was looking for, pretty much:

Brushing means selecting a subset of the data items with an input device (mouse). This is usually done to highlight this subset, but it can also be done to delete it from the view or to de-emphasize it, if the user wants to focus on the other items.

Original here.