A public chat room is a place where any user in the project can join and participate in the chat. On the other hand, a private chat room is visible only to its participants. You can specify which type of chat you want when you create it. This can also be changed at a later stage.

You can also have individual chats with any user in the project. To initiate such a chat, just click on the user you wish to chat with in the 'People in this project' list, in the right margin of the Dashboard module. You can also select a user form the 'Available project users' list in, the right margin of the Users module.