I'm not terribly versed in web page elements. I was wondering how japaneseclass.jp was able to automatically fetch news website articles, parse the vocabulary in each article and list definitions. (example: http://japaneseclass.jp/readings/read/322740). It even has a vocabulary quiz arranged by multiple choice (accessible after creating an account and logging in).

It would be useful if I could use the same resource to quiz myself on vocabulary, found in other web articles of my choosing.

Its not a "web page element" that does that.

The automatic fetching, parsing, and creating lists; happens on the backend (ie: the server).

They are probably using a Python or Node.js server to do this, but you could technically accomplish the same thing on an Apache/PHP server (CRON jobs) or a Java based web server. The lack of a file ending in the URL (look at the forum, notice the viewtopic.php?) would suggest a servlet based server though like Python/Node/Java.

EDIT: Might be possible in Ruby as well, though I don't know how Ruby on Rails works on the backend.

This is a cool website! I've actually spent some time thinking that some functionality like this would be very useful for learning. It's good to see someone actually made it.

I think OP isn't asking specifically what software the server is running, but rather if there is some software he could use at home to do the same thing. If this is what you are looking for, you might take a look at jglossator. It doesn't automatically fetch news articles, but it will create definitions for any japanese text you copy to the clipboard.

Does it only take part of the news article? or can you get it to show the whole thing?