According to Microsoft Support, the main function of the session layer is to establish connections, otherwise known as sessions, between processes running on different computer terminals or Web-enabled devices, referred to as stations. The session layer is the third layer from the top in the seven layers of the open systems interconnection model that conceptually characterizes and standardizes the internal functions of modern communications systems.
Above it, there are the application and the presentation layers. Below it, there are the transport, the network, the datalink and the physical layers. In addition to its main function, the session layer is also responsible for communicating with the presentation layer above it and interpreting the transport layer below it. An example of the session layer in action would be how each of the individual objects, including graphics, Java applets and text required to load a Web page, are downloaded in the browser from a Web server. To render the Web page, the browser needs to access each of these individuals file separately and then reconstruct the website on the browsing device. This requires the browser to open individual sessions for each of the files, download said files and then terminate the session. During this process, the session layer keeps track of which data packets belong to which file to avoid data corruption.