The OSI model defines 7 layers of network communication, with layers 1-4 relating to communications technology and layers 5-7 relating to user applications. The physical layer deals with transmitting raw bits over a physical medium, the data link layer packages bits into frames and provides reliable transmission, the network layer handles addressing and routing between networks, and the transport layer manages transmission of packets and error checking. Higher layers include the session layer for establishing connections between applications, the presentation layer for translating between data formats, and the top application layer for software applications to access network services.