The people you're closest with, and the ones who are getting there.
The Starred group is a collection of your closest relationships, created during onboarding. You can edit who belongs in this group by opening their card and toggling the on Mac or Web or by hitting StarS. Adding or removing people works the same as with other groups.
Keyboard Shortcuts
G then 1-9 to open a Group
G then S to open Starred
When you have a Group open
E to edit to change the color or name
A to add people
In a card
S to star or unstar
L to add to a group