"The Open Systems Interconnection model (OSI model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to their underlying internal structure and technology. Its goal is the interoperability of diverse communication systems with standard protocols. The model partitions a communication system into abstraction layers. The original version of the model defined seven layers."
Here are a few videos to help explain each of the layers.
Understanding the OSI Reference Model: Cisco Router Training 101
The OSI Model Animation