Seasoned computer scientists, engineers, and software developers all know that one of the subtler and trickier problems that arise in our industry is naming. It sounds a bit silly and it is repeatedly the subject of jokes, but the difficulty remains—how do you speak or write explicitly on a subject whose very nature requires exquisite precision and yet has great ambiguity that arises in different contexts?

We have the same problem with the term backend. Here, as in so many other instances, the context is everything. Our context is matplotlib, a set of tools, and a framework where everything is done in support of the visualizing of data and their relationships. The term backend has to be viewed from this perspective to support the generation of plots. The matplotlib backend has nothing to do with other noteworthy backends such as databases, servers, messaging systems, or dispatchers of various sorts. The backend of matplotlib is an abstraction layer over various components...