Layer 7: The Application Layer

The top layer in the OSI Reference Model is the Application Layer. Despite its name, this layer does not include user applications. Rather, it provides the interface between those applications and the network’s services.
This layer can be thought of as the reason for initiating the communications session. For example, an email client might generate a request to retrieve new messages from the email server. This client application automatically generates a request to the appropriate Layer 7 protocol(s) and launches a communications session to get the needed files.