The Nextcloud Teams group sharing function was formerly called Circles
Nextcloud teams are provided by the Nextcloud Teams App. Teams allow your users to create their own groups of users/colleagues/friends. Those groups of users (or 'teams') can then be used by other apps for sharing purpose (files, calendars, tasks, forms, decks, …).
Teams provide the following configuration options:
Anyone can request membership
This option allows any user who can see the team to request membership. This is dependent on Visibility options.
Members need to accept invitation
This applies to users you add as members to the team. The invite will appear as a notification for the invited user under the bell icon in their Nextcloud interface. If they choose to accept they will be added to the team.
Memberships must be confirmed/accepted by a Moderator (requires Open)
If you've allowed anyone to request membership you must accept their request before they can join the team. This does not apply to members you add directly.
Members can also invite
This allows any member of the group to add other members to the team.
Enforce password protection on files shared to this team
This only applies to files and only applies to e-mail contacts added to the team. The password will be sent by e-mail automatically. Other Nextcloud users who are added directly as members of the team will not need a password.
Use a unique password for all shares to this team
Every file or folder shared with the team will have a different password associated but the same conditions above apply.
See related pages:
How to create a Nextcloud team