See also the official documentation:
Status Badges in the Members List
In the Members List some rows have status badges after the member's email address. These badges also appear on the Your Groups page at https://groups.io/
Here's what they mean.
The email status of a subscribed email address is determined automatically by the system. There is generally nothing the group owners or moderators can do about the status other than encourage the member to take action. See the details below for the exceptions in a Premium group.
(no badge) - Normal status.
Bouncing - Groups.io has stopped delivering group messages to this address, but is attempting to contact the address.
Bounced - Groups.io has given up trying to contact this address.
Not Confirmed - User needs to respond to the email confirmation letter sent by Groups.io.
For more about how delivery to email addresses is tracked by Groups.io see Bounce Handling on the Help page. The process is designed so that the group admins need not take any action to administer the addresses which have bouncing or bounced status. Removing the "bounced" addresses from the group is purely optional. Two things the group admins can do is generate extra "bounce probe" notifications to the address, in hope that one of these will be acted upon, or if the admins have an alternate means of contacting the individual who owns that address they can attempt to inform the person of the situation.
In certain circumstances an individual may attempt to join a group without having first confirmed to Groups.io that they are the legitimate user of the subscribing email address. In such case the email address is initially given Not Confirmed status, and no group messages will be sent to that address until the user confirms it.
1) When an individual attempts to join a group by using the group's +subscribe email address Groups.io will send back to their address a confirmation request notice. The notice requests that the recipient reply to confirm their desire to join the group. That person's email address does not appear in the group (not even in the Activity logs) until the user replies to the confirmation request. After the user replies to the confirmation request their address is not assigned NC status.
2) When an individual who is not logged in to Groups.io attempts to join a group by using the group's home page button the address is initially assigned NC status. The Groups.io web site will prompt them to log in. Logging in, using any of the available methods, will remove NC status. The group admins may have Groups.io send confirmation requests by email if desired. In a Premium group with restricted membership the group admins may approve the member's subscription and that will also remove NC status.
3) When an individual who is logged in attempts to join a group by using the group's home page button their address is not assigned NC status.
4) In a Premium group addresses may be added to the group via Direct Add. These addresses are not assigned NC status.
5) Addresses added to a group via transfer from a Google Group or Yahoo Group are not assigned NC status.
The individual who creates a group is initially assigned the Owner role. All individuals subscribing thereafter are initially assigned the Member role.
(no badge) - This user is a member of the group.
Moderator - This user is a moderator of the group.
Owner - This user is an owner of the group.
Owners may reassign the role of any subscriber, including that of other owners, and may change the permissions granted to individual moderators.
Moderators may be granted the permission to "Set Moderator Privileges", such moderators may change the permissions of other moderators, and their own, and they may reassign members to moderators, or moderators to members.
NOTE: If you are logged in with an account that is a Moderator or Owner of a group, the corresponding badge will also appear on the Home button in the left-side menu bar.
The individual who creates a group is initially assigned the Default group policy as their Posting Privilege. All individuals subscribing thereafter are assigned an initial Posting Privilege that depends on the "New Members Moderated" checkbox in the Spam Control section of the group's Settings page. If that box is checked they are assigned New Member Moderated, otherwise Default group policy.
(no badge) Use Group Moderation Setting.
Can Post - Override: not moderated.
Moderated - Override: moderated.
New Member Moderated - Override: new member moderated, count of messages to approve.
Cannot Post - Override: not allowed to post.
Moderate First - Override: moderate the first message of every topic this person starts.
Moderate Topics - Override: moderate all messages of every topic this person starts.
See Member Controls in the Message Moderation wiki page for details on the Posting Privilege controls.
In accord with https://beta.groups.io/g/main/message/19069, a subscriber who has chosen any of the Advanced Preferences for email delivery will display corresponding badges in this column.
(no badge) No Advanced Preferences selected.
Following Only w/ First Message Also
Auto Follow Replies
Max. Attachment Size limit (any selection except Unlimited)
These Advanced Preferences can be found (and changed) in either the member record or the member's Subscription settings. See these Help Center topics for details: