The site itself doesn't provide any live conversation possibilities. Even when you book a lesson with a teacher, the actual talk usually takes place over Skype; Italki basically is only there for the organization (scheduling, money) and provides both of you with each other's contact data once the session is scheduled. There is an internal message system, though. Some people have configured their account so that anybody can send them messages, for others you have to "follow" each other first before messages are enabled. Once you have established some contact this way, you can exchange your Skype data to have live chats.