Here's some note from a recent email that @Halfak sent:

Edit quality -- This is what you have enabled by finishing labeling edits as "damaging" and "goodfaith". The models we'll build will be useful for patrolling for vandalism and other types of damage. We already have integrations ready in Special:RecentChanges, Huggle, and a few other patroller tools.

Article quality -- These models are used to determine the overall quality level of an article. This is often used to track progress towards high quality, to measure coverage gaps (by comparing predicted quality to view rate), etc. When setting up models like this, we want to work with the local wiki community's notion of quality. Often a wiki community has already set up a quality scale with something like English Wikipedia's "Featured Article" at the top and something like "Stub" at the bottom. We can sometimes train a model based quality tags that Wikipedians have already placed on existing articles, but if there aren't enough labels or they aren't consistent enough, we can set up a labeling campaign (like what you did for "edit quality") in Wiki Labels. Currently, the only cross-wiki integration that we can provide is the ArticleQuality.js gadget (that I have poor documentation for because I've developed it in my volunteer work). This gadget allows you to look at quality predictions over the history of an article on the history page, it will tag lists of article links with their quality-level so that contributors can prioritize work, and it will add quality predictions to the top of article pages just under the title.
(c.f. Page level)

Draft quality -- These models are designed to detect obvious problems with new article creations ("drafts"). Specifically, we target "Spam", "Attack pages" and "Vandalism". We've built this model for English Wikipedia using their Criteria for Speedy Deletion. Currently, this model is used in Special:NewPagesFeed which is, regretfully, an English Wikipedia-only extension. But there are rumblings among WMF Product to either extend the extension to other wikis or to develop something new that will work cross-wiki.

Draft topic -- This is our newest, most experimental model. It is designed to help route new page creations to reviewers who are interested and likely have expertise in the topic's subject matter. The goal here is to route the new articles to experts for review. Right now, there are no implementations. See me presenting on our vision for how this model would be used at Wikimania: https://commons.wikimedia.org/wiki/File:Using_AI_to_keep_Wikipedia_open.webm