What is the difference between 1:1 Chat Room, a Private Group Chat Room and a Public Group Chat Room? The difference is in the numbers.
With a 1:1 Chat Room, you select a specific HeyPeers user, you created a connection with, to enter into a private chat room between the two of you.
With a Private Group Chat Room, you create a chat room - creating a name and description of the chat room. You then invite specific HeyPeers users, you created a connection with, to enter into a private chat room between those invited.
With a Public Group Chat Room, you create a chat room - creating a name and description of the chat room. You can invite specific HeyPeers users, you created a connection with, to join the public chat room if you believe it would be beneficial for them. Be sure to click on the box next to "Make this chat public" when creating the chat room. It will then display on the public list of chat rooms on the Chat page.