Threads displays a timeline of related posts.
If you have ongoing themes you write about on your site, you can use Threads to show those posts in a timeline, with a link to the timeline from each of the posts. This helps you avoid feeling like you have to rehash too much history about the topic in each post.
Another good usage of Threads is on a news site to track posts related to a single ongoing story. For example, a tech blog might create a thread to group stories about a product launch event. Several months later, stories about sales figures for the product might be added to the thread. By placing all of these posts in a thread, there is a useful visual way of browsing all of the posts.
The timeline display of a thread is both responsive and retina (HiDPI) friendly. See an example here.
Developers, please contribute on GitHub.