Most of the interaction between people within a Manhattan classroom is asynchronous. That is, students and teachers do not have to be logged in to Manhattan at the same time in order to exchange messages. As the teacher, you may post a new discussion topic in the Class Discussion module on a Sunday evening. A student may read the message Monday morning and post a reply. You might read the student's contribution later that day, and post a follow-up comment the next morning and so on. This method of exchanging messages over a period of hours, days or even weeks is not foreign to anyone who uses ordinary Internet e-mail or even traditional paper letters dropped into the corner mailbox to be delivered by the Postal Service.
In contrast Manhattan's Chat module, which is a lightly modified version of Christian Walter's Melange Chat, is a synchronous communications medium. In order for two people to exchange messages using Chat, they must be logged into Manhattan and be in the Chat module at the same time. While the other modules are analogous to Internet e-mail, Chat can be compared to a telephone call when there are only two people chatting, or to a conference call, if there are several people in the Chat room.
Because of the synchronous nature of Chat, it is always best to schedule a Chat session. Unless everyone knows in advance when a Chat session will take place, the chances of meeting someone in Chat are slim. As the teacher, you should post a message in say, the Handouts/Notices module, announcing the date and time of the Chat sessions. Students are also free to meet with each other in Chat without you. In that case, they can schedule their own meeting times using for example, the Class Discussion, the Post Office, or the Team Discussion module.