Each Rich Text Field is, in fact, a full-blown collaborative text editor. Work on the same document with multiple people in real time and see the changes immediately.
You can insert various blocks into the text as well:
@mention a User
Image
Table
#link an Entity (reference to Task, Document, Feature, etc)
Quote
Code block
Checklist

Format text with a popover menu or by typing markdown (**bold**):

And add comments to discuss anything:
