A public meeting type is one where anyone who has the URL for the meeting can enter the room.

A private meeting type is one where only registered users and participants can enter. The login page does not allow guests to log in. With private meetings the meeting does not actually start until the meeting Presenter or Host joins the meeting.

If you are creating a private meeting it is always good practice to assign at least 1 host or presenter who will be present in the meeting; because users with the participant role will be unable to join the meeting unless a user with the host or presenter roles has already joined th meeting.

If the meeting has support for separate groups at least 1 user in each group, who is to be present in the meeting, should have either the host or presenter role.