Invite-only threads
Threads that exist outside of a group are now called "invite-only threads" throughout the interface.
How it works
You can start a thread and invite specific people without attaching it to a group. These threads are visible only to the people you invite, and they show up on the invited members' dashboard under "Invite-only."
Terminology
All references to "direct threads" in the interface have been replaced with "invite-only thread" to better describe how they work.