A group conversation is a persistent chat room and shared file folder available exclusively to invited members of the group. Groups are never announced publicly or visible to anyone beyond its members. Only invited members have access to the group conversation, know of its existence, and see who else is a member.
The person who creates the group is the group owner. The owner can add and remove other members.
The owner can also promote other members to operator. The operator can also add and remove members.
Only the owner can delete the group.