This is a new feature I'm experimenting with. The idea is that you can use keys to navigate the "list tables" in the WordPress dashboard. These are things like the post list, plugin list, user list, etc.
The current keys you can use are:
These keys are the same as the vi(m) editor, and a bunch of other things. But the whole idea was really inspired by the notifications navigation on github.com, which I use keys to navigate.
This feature is VERY basic right now, but it will evolve. Stay tuned!