The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven distinct layers. The Physical layer is the first layer, handling the transmission of raw binary data over physical mediums like cables. The Data Link layer ensures error-free data transfer between two directly connected nodes by organizing bits into frames. The Network layer is responsible for routing data packets between devices across different networks. The Transport layer ensures reliable data transfer with error detection and correction. The Session layer manages and controls the connections between computers, maintaining sessions for ongoing communication. The Presentation layer translates data between the application layer and the network, handling encryption, compression, and data formatting. Finally, the Application layer provides network services directly to end-users and applications, such as email, file transfer, and web browsing.