There are two types of chats:

Personal chats - Personal chats are private and visible only to users who you have added to the chat's participants list. Personal chats are ideal for keeping in touch with friends and colleagues or for clubs and other groups whose members do not share a single org unit. Anyone with the proper permissions can create personal chat rooms.
General (unit) chats - General chats are public chats visible to everyone enrolled in the org unit where they are created. Instructors can create general chat rooms to incorporate chat discussions into the teaching of a unit since they are automatically open to all users enrolled in the unit.

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