Networking is the ability to exchange data between two or more applications across two or more computers. Because each computer on the network may be different (a Macintosh, a PC, a Sun workstation), networks must not only transport data, they must translate protocols between dissimilar computers to assure compatibility at the hardware and software level.
To conceptualize the many translation steps required by the network server to successfully link computers, we can use the OSI network model. The model's purpose is to outline the logical processes required to exchange data between potentially dissimilar computers on a network.

The OSI (or Open Systems Interconnection) model conceived by the International Standards Organization (ISO), a U.N. agency, is a seven-layer framework for implementing protocols or tasks. The following SlideShow shows the function of each layer.

OSI Reference Model
In the next lesson, the infrastructure of the Internet will be discussed.
The link below discusses the layers in the OSI model.
OSI Network Components