The Session Layer is the fifth layer of the OSI model, which is a framework used to understand network communication. Its primary function is to establish, manage, and terminate sessions between applications. This layer ensures that data exchange is organized and synchronized, allowing for smooth communication between different systems. In addition to managing sessions, the Session Layer also handles the control of dialogues, which can be either half-duplex or full-duplex. This means it can manage one-way or two-way communication, ensuring that both parties can send and receive data effectively during their session.